Method for producing a highly stretched multi-layered film

ABSTRACT

A method for producing a high strength multi-layered film excellent in heat resistance, shrinkability and stretchability and usable for wrapping of various articles which comprises at least five layers comprising a surface layer (S layer) mainly composed of at least one polymer selected from (A), (B), etc. and as inner layers at least one base layer (SBC layer) containing mainly a mixed composition comprising a combination such as (A)+(B)+(C), at least one core layer (H layer) containing mainly a polymer selected from (C), and at least one auxiliary layer (R layer) containing mainly at least one polymer selected from (A) and (B), with a proviso that when the R layer is placed-adjacent to the S layer, the R layer comprises the resin different from that of the S layer, said (A) being a low-density polyethylene or a copolymer of ethylene with a specific monomer, said (B) being a soft thermoplastic elastomer having a Vicat softening point of 80° C. or lower, and said (C) being a specific polymer such as a crystalline polypropylene or the like or a mixed polymer thereof.

This application is a divisional of application Ser. No. 07/863,307,filed on Jul. 13, 1992, the entire contents of which are herebyincorporated by reference now U.S. Pat. No. 5,300,353.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a multi-layered film (oriented andimparted with high strength) for use mainly in a wrapping materialfield, and its modified film (orientation degree control by heattreatment, crosslink by energy beam or other chemical treatment). Morespecifically, it relates to an at least monoaxially stretched/oriented,high-strength, multi-layered film excellent in heat resistance,shrinkability and stretchability, which has a layer constitution of atleast five layers comprising at least one base layer (SBC layer) mainlycontaining a specific mixed composition to improve the stretchability,at least one core layer (H layer) composed mainly of at least one hardpolymer selected from crystalline polypropylene, crystallinepolybutene-1 and crystalline poly-4-methylpentene-1, the core layerbeing to improve the elastic modulus and heat resistance of the film, atleast one auxiliary layer (R layer) for the purpose of furthersynergistically improving the strength of the film, and surface layers(S layers) to improve the optical properties, anti-figging property andsealability of the film surface.

The film of the present invention can be used not only for shrinkwrapping, stretch wrapping and stretch-shrink wrapping but also for skinpack wrapping, tight-contact household wrap, nonshrink wrapping, softdeep-drawn wrapping and the like.

TECHNICAL BACKGROUND

In film wrapping, a variety of wrapping methods taking advantage of thefilm properties are used. For example, many methods are used such as amethod of sealing in a bag form, a method of wrapping by twisting afilm, a method of wrapping by heat shrinking (to be referred to as a"shrink method" hereinafter), a tight-contact wrap method typified bySaran Wrap® (made by Asahi Chemical Industry Co., Ltd.), a stretch wrapmethod and a skin pack method. Each wrapping method is required to haveits own wrapping properties, and in a practical sense, film materials,composition, form and properties are selected suitably for each wrappingmethod.

Of the above methods, the shrink method uses the heat shrinkability of apreliminarily stretched and oriented film. In this method, an article tobe wrapped is preliminarily loosely wrapped by a film, for example, anarticle is wrapped by sealing, and then the film is allowed to shrink byheating it with hot air, infrared rays, hot water or other heatingmedium to bring the film into tight contact with the content containedtherein. The characteristics of this wrapping are that the appearance ofthe wrapped article is esthetically good, that the commercial value isimproved, that the content quality can be visually and tangiblyrecognized while the article is kept in a hygienic wrapping, that evenan irregularly-formed article and even a plurality of articles can betightly fixed or wrapped in one wrapping, and that the protectionperformance for the content against vibration and impact is excellent.Further, as compared with a stretch wrapping method which is popularnowadays in supermarkets and will be described later, the above shrinkmethod characteristically permits an increase in wrapping speed. Theshrink method also permits the wrapping of an irregularly formed articlewhich cannot be wrapped esthetically by a stretch wrapping and of anarticle without any container such as a tray. Moreover, the shrinkmethod characteristically permits the wrapping of various articles moretightly. However, on the other hand, the shrink method has defects inthat the film is required to be sufficiently heated until the filmbecomes shrunken. This would result in the likelihood that the sealingportion would break and that the film would deteriorate after beingshrunk (strength and optical properties). On the other hand,conventional shrink films have low stretchability, and would break ifstretched, to any large extent. Some conventional shrink films cannotsimply be stretched due to too strong of a stress caused by thestretching. Further, these films have almost no self-adhesionproperties. For these reasons, these shrink films are not at allsuitable for stretch wrapping. Conventional shrink films have theabove-described defects and problems.

As long as the above defects can be overcome, shrink wrapping is moreadvantageous than stretch wrapping in use of film area a film, in lesserfilm thickness and in wrapping speed.

Meanwhile, stretch wrappings have the following excellentcharacteristics. An easily stretchable film is rich in fitness in whichit is free from permanent deformation and the tendency to form a creasewhen stretched and it can cope with the concavo-convex form and size ofan article to be wrapped. A film can be simply fixed by a wrappingtension without loosening by lightly attaching it under pressure orheat-sealing it. A film for fresh foods has proper permeability to gasto prevent the decrease in freshness and weight. The quality of anarticle can be visually and tangibly known while the article is kept ina hygienic wrapping. The appearance of a package is esthetically goodand the commercial value of a wrapped article can be remarkablyimproved. A wrapping machine can be selected from less expensive manualwrapping machines and high speed automatic wrapping machines asrequired. Further, an article to be wrapped is not at all heated. As awrapping method having the above excellent characteristics, the stretchwrapping method is widely used in supermarkets, etc., for wrappingfruits and vegetables, fresh foods, meat and cooked dishes. However,films for the stretch wrapping have the following defects and problems.Due to having low strength, the film is likely to break mechanicallyduring wrapping or in distribution. The film is likely to form holeswhen sealed. Since the film is imparted with stretchability by takingcare not to give too stretch and orientation when produced, the film ischaracterized with a low modulus of elasticity. The film thicknesscannot be extremely decreased as a result of the importance placed onits operational capabilities (e.g. mechanical suitability and manualworkability) (in order to avoid deteriorating these capabilities), andaccordingly, a film having a large thickness is inevitably used. Manymanufacturers have attempted to create films equivalent to or filmswhich are excellent over conventionally widely used films formed ofplasticized vinyl chloride (containing 30 to 33% by weight of aplasticizer), and these manufacturers have manufactured a variety offilms from various resins by way of trial. However, up to the presenttime they have not been successful. From the viewpoint of environmentalpollution and hygiene, it has been desired to develop a substitute filmfor the plasticized vinyl chloride film. However, the use of filmshaving inferior qualities and being poor in handling properties isunavoidable at the present time. However, these substitute films beingused at present are poor in handling and are used with reluctance in aworking site due to their poor wrapping workability. These substitutefilms are not used in such amounts that they can replace vinyl chloridefilms. Presently, the amount of these films which are in use is verysmall.

The shrink wrapping is explained hereinafter, which, of course, does notlimit the present invention.

As for shrink wrapping, a stretched film of plasticized polyvinylchloride (to be referred to as PVC hereinafter) is used in the largestquantity as a high-class shrink wrapping film. This film has superioradvantages in that it is capable of heat shrinkage at a high rate and ata relatively low temperature. It permits excellent shrink wrapping in awide temperature range, and also has a high film elastic modulus (50 to200 kg/mm²) and excellent suitability to mechanical wrapping. However,it is inferior in heat sealability and in moisture proof, and it has ahygienic problem due to the presence of a plasticizer and a problem ofdeterioration with time due to the plasticizer. There are also problemsin that it generates a toxic gas such as a chlorine-containing gas whenfused with a heating wire for cutting. It also generates a corrosivetoxic gas when incinerated after use, and it also becomes stiff andfragile and is likely to break due to having poor resistance to coldwhen a wrapped article is preserved at a low temperature, handled in acold area or frozen.

In recent years, a polypropylene-based (to be referred to as PP-basedhereinafter) shrink wrap film has been attracting attention. The defectwith this film is that the shrinkability is inferior to that of a PVCfilm. A PP-based stretched film is superior in mechanical properties,moisture resistance and fusion-sealability and excellent as a shrinkwrapping film. Further, it has a lower specific gravity than PVC, and isadvantageous in terms of material cost.

However, PP is a crystalline polymer having a high softening point, andlikely to tear when stretched. Moreover, it has a higher heat-shrinktemperature than a conventional stretched film, particularly a PVC film,and shows a small shrinkage at a lower temperature of about 100° C. Forthis reason, PP is required to be heated to a higher temperature in ashrink wrapping step. The tolerable range of the heating temperature isnarrow, and further, the dependence of the shrinkage on temperature issharp. Therefore, due to a local uneven heating during the wrapping, itshrinks unevenly to cause undesirable defects, such as "creases" and"pockmarks" in the course of practical use. If the pp film issufficiently heated to prevent the above defect, undesirably, an articleto be wrapped would become over-heated, and the PP film would undergodevitrification, form holes by being melted, deteriorates in performanceand would result in a large breaking which starts from a sealing portionor an air-discharge opening portion. These constitute serious defects. APP film also has defects in that a wrapped article is likely to be loosesince a stress is released after a certain period of time and the filmafter wrapping becomes hard and more fragile.

In a conventional polyethylene-based film, the molecule cannot besufficiently stretched or oriented. Therefore, such a film has a lowheat shrinkage, a low heat shrink stress in particular. Further, thefilm has a high shrink temperature, and it is also inferior in strengthand optical properties. The strength of the film binding a wrappedarticle is also low. Therefore, the film having an increased thicknessis used in a special field.

The polyethylene-based film, which is obtained by using high energy raysto cause a sufficient crosslinking reaction on the molecule and bystretching it at a high temperature, has a high heat shrinkage and ahigh heat shrink stress in a high-temperature range, and such a film isexcellent before wrapping over a general polyethylene-based film inoptical properties such as transparency and gloss and heat resistancesuch as melt resistance or resistance to formation of holes. Since,however, it is allowed to shrink in a high-temperature range, itsperformance greatly deteriorates as compared with a film used for shrinkwrapping at a low-temperature (particularly, the optical propertiesgreatly decrease). Furthermore, the above film has a defect in that thewrapping speed is inferior for the following reasons. It has heat shrinkproperties in which it rapidly shrinks under heat. It is difficult toheat-seal due to high crosslinking. It is easily broken due to inferiorresistance to tearing, and difficult to cut with a heating wire. Asdescribed above, to maintain the performance of a film, one of theimportant features required of shrink wrapping is that the wrapping canbe carried out effectively at a low temperature, and this feature isalso required when an article to be wrapped is brought into contact withthe film (particularly when fresh foods are wrapped).

In case that a known film which has a high shrink temperature (it ispractically required to allow the film to shrink at least 20% in thewidth and length directions), or which shrinks rapidly under heat (dueto high shrink dependency upon temperature) is used wrapping is requiredto be conducted at a temperature greatly exceeding the melting point ofthe polymer and under very narrow conditions in order to particularlyimprove the finish of a wrapped article. This case involves acontradicting problem in that the properties of the film are greatlydecreased.

On the other hand, when a stretched film is produced from PP as amaterial, there is employed a method in which PP is melted in anextruder, extruded through dies and rapidly cooled to obtain a film(hereinafter referred to as "raw film") in a tubular form, the tubularraw film is reheated at a high temperature of 130° to 150° C., andstretched by introducing air into the tube. When the material is alow-density polyethylene, it is considered that biaxial stretching forhigh stretching and orienting easily causes breaking at a processingtime and that the stretching is technically very difficult.

For this reason, it is a general practice to employ a one-stageinflation method in which the material is extruded, e.g., at atemperature of 180° to 220° C. and then immediately inflated whileproperly cooling it with air to form a film having a predetermined size.

The above method has a characteristic feature in that the film can beproduced at a very low cost with ease. However, intermolecular flow islikely to occur, and no satisfactory molecular orientation can beobtained by stretching. Further, the film shows very poor opticalproperties. Therefore, the heat shrinkage and heat shrink stress aresmall, and the heat shrink temperature region is on a high-temperatureside. Only when the film has an increased thickness, can it be used in aspecial field. For this reason, it is conceivable to prevent theintermolecular flow and obtain a sufficient molecular orientation byemploying a method which comprises forming a low-density polyethylene,irradiating the formed product with high-energy radiation under properconditions to cause a partial crosslinking reaction, reheating theproduct up to a temperature beyond the melting point (e.g., 140° C.) andstretching it. In this case, however, the degree of the shrinkage is lowat a lower temperature, and the resultant film is likely to tear.

For other new wrapping film, a diversity of composite, multi-layeredfilms are known.

With a technical advance in required properties, an increasing number ofcomposite films tend to be produced. For example, there is a compositefilm obtained by melt-laminating other resin on a nearly unstretchedfilm or a stretched film. Specifically, commercially available is a filmhaving improved heat-sealability obtained by melt-laminating other resinon an unstretched polypropylene prepared by a casting method (calledCPP) or an oriented polypropylene (OPP) or a film which is coated withvinylidene chloride-based latex to impart it with barrier properties(called K coat film). A variety of films or a combination of these filmsare selected depending upon use.

On the other hand, generally known is a co-extruded film obtained bymelting a plurality of resins in separate extruders, extruding theresins through a multi-layer die while converging and fusing them insidethe die and cooling the resultant product to form a film or sheet.

However, when a film having the above multi-layer structure of which atleast one layer is highly stretched and oriented is obtained from acombination of resins having mutually different properties (meltingpoint, softening point, melt index and orientation properties), theoptimum extrusion conditions and stretching conditions differ dependingupon the resins. Therefore, when such a film is produced by a prior artmethod, many problems occur including defective phenomena such as anonuniform section, streaks including an insufficiently stretchedportion, a puncture, breach, peeling of layers and whitening due tointerfacial toughening. Further, there is obtained a film havingdifferent properties from those of an intended film. Thus, these defectshave not yet been overcome. In order to overcome these defects, thepresent inventors completed composite films, which are disclosed in JP,A55-118859 (corresponding to U.S. Pat. No. 4,430,378) and JP,A 58-175635.However, these films have not as yet sufficiently met the aboverequirement level. The present invention has achieved the creation of afilm which fully satisfies the properties lacking in these compositefilms, which widens the use field, and which is capable of exhibitinghigh performances even though it has a much smaller thickness than anyconventional film and is excellent in cost performance. These featureswill be more clear in comparison made with the Comparative Exampleswhich will follow later.

The present status of the stretch wrapping, a second field to which thefilm of the present invention is directed, will be describedhereinafter.

In this field, films formed from a soft PVC containing, as a material, alarge amount, e.g., as much as about 30% by weight (nearly 50 vol %) ofa plasticizer are mainly commercially used. If a large amount of aplasticizer is not incorporated, it would be difficult to process thesefilms, or it would be impossible to impart the film with flexibleproperties, and these films could not be used in this field. Since alarge amount of a plasticizer, such as DOP, DOA, etc., is incorporated,these films would have the problems in that the amount of permeatingwater vapor would increase, and a wrapped article would likely bealtered, that these plasticizers would likely migrate to a wrappedarticle thus contaminating the article, that a gas of the plasticizerand a corrosive chlorine gas would be generated when the film is fusedduring a wrapping work, which would be hygienically undesirable, that atoxic gas would be generated when a used film is incinerated, and thatthe film would become less flexible and fragile and would be likely tobreak due to its poor resistance to cold when a wrapped article ispreserved at a low temperature, which is as already described.

Meanwhile, single-layered films formed of a high-density polyethylene, alow-density polyethylene and a PP-based polymer among the generallyusable polyolefins have excellent properties over the above defects.However, these films do not have the other important properties requiredfor use in the field to which the present invention is directed to. Ithas not been possible to form a practically usable stretch wrapping filmwhich satisfies all of the following characteristics as a wrapping film.That is, any film for use in stretch wrapping is required to satisfy thefollowing properties simultaneously.

a. The film is to be excellent in film-film adhesion.

b. The film is to have a proper degree of (excellent) recoverabilityfrom deformation, a proper degree of elastic elongation and highmechanical strength.

c. The film is to have a proper degree of lubricity.

d. The film is to be excellent in optical properties such astransparency and gloss.

e. The film is to a proper degree of gas permeability.

f. The film is to retain no water drops and to be excellent inanti-fogging property.

g. The film is to be excellent in wrapping workability.

h. The film is to have heat resistance sufficient to endure heat insealing.

For example, when an unstretched film of PP is stretched, it causes aphenomenon called necking, that is, it is locally stretched and thethickness becomes extremely nonuniform. Even after a load is removed,the stretched portion remains as is. Therefore, the appearance of awrapped article is extraordinarily impaired, and the purpose in wrappingis not achieved. A stretched film of the same is hard, strong and littleextendable so that a very large force is required to extend it, and anarticle being wrapped would be destroyed. This film is also without anyadhesion properties, and it is therefore required to incorporate as muchas 5% by weight of a plasticizer such as low-molecular-weight polybutenein order to impart it with stretchability and adhesion properties. Inthis case, however, since polyolefin is, unlike PVC, not at all capableof retaining the plasticizer, most of the plasticizer bleeds out on thesurface and makes the surface sticky, and such a film is not suitablefor practical use.

A high-density polyethylene is also too hard to simply stretch. Even ifstretched forcibly, it causes a nonuniform thickness due to necking, andresults in a similar result. Further, it is all opaque or without glossand cannot be put to practical use.

Films formed from low-density polyethylenes are much softer than theabove film. However, unstretched films of this type cause a neckingphenomenon in packaging, and they have little recoverability fromdeformation, low strength, low transparency, film-film adhesion propertypoor and a problem in practical use. Therefore, they cannot meet theobject of the present invention. Further, when these films aresufficiently stretched (e.g., at an area stretch ratio of 20 times) at atemperature equal to or higher than the melting point according to aconventional method after imparted with a crosslinked structure byelectron beam and rendered easily stretchable, the resultant films havethe same defects as those of PP, and they cannot be used as a substratefor stretch packaging which is an object of the present invention.

A film formed from an elastic elastomer having nearly completerecoverability from deformation such as a styrene-butadiene copolymerand a rubber substrate formed from other material is free from aphenomenon of said necking. However, such a film has problems concerningoptical properties and hygienic storage of food. Besides these, thestress strength of elongation is nearly completely in proportion to thedegree of elongation, and the response in recovery from deformationinstantaneously occurs without any delay. There is therefore a problemin that the film takes its original shape immediately before the endportion of the film is set under an article to be wrapped or a tray.Thus, such a film has properties due to which it can be hardly employedfor the use of the present invention.

Of these polyolefin-based films, those that are produced by mixing amain component such as linear low-density polyethylene, particularly anultra-low-density polyethylene, crystalline 1,2-polybutadiene and anethylene-vinyl acetate copolymer (EVA) with an anti-fogging agent and atackifier and by forming the resultant mixtures into films byconventional methods (T-die method and air-cooling inflation method) areon trial in the market. However, these films have many of the defects asdescribed above, and presently have not as yet arrived at the level ofreplacing conventional films.

These films cannot satisfy all of properties which are mutuallycontradicting such as easiness in elongation in wrapping, heatresistance of a sealing portion, easiness in sealing and prevention ofbreach in wrapping caused by insufficient film strength, and haveunsatisfactory properties. For example, in an EVA film, it is requiredto increase the content of vinyl acetate (VAc) in EVA in order to makethe film easily elongated. In this case, however, the bottom portion(under the tray) tends to be melted under heat and becomes broken insealing. To prevent this, it is required to increase the film thicknessfrom 16 μm up to 20μ, 22μ or 24μ. When the film thickness is increased,however, the defects of the film also increases. That is, it isdifficult to elongate the film, the film hardly adheres to the filmbefore sealing, and the film is likely to break due to its decreasedstrength. Further, the film cost disadvantageously increases.

When other polymers, particularly a low-density polyethylene(particularly a linear type one) or PP-based rubber is incorporated,another problems arise. That is, the important properties such astransparency and gloss tend to be decreased.

DISCLOSURE OF THE INVENTION

The present inventors have made a study to overcome these defects of thefilms. As a result, they have succeeded, for the first time, in greatlyimproving the films in heat shrink properties, particularly in heatshrink properties at a low temperature, heat shrink stress, widening oftemperature dependence of heat shrink properties, optical properties,heat sealability of films, elongation properties and strength alltogether, and arrived at JP,A 60-79932 (corresponding to U.S. Pat. No.4,619,859). This film has a lower elongation stress than that in theaforedescribed JP,A 58-175635 and is excellent over any existing film instretchability. However, in order to improve the function, performanceand cost performance, it is required to satisfy contradicting propertiessuch as strength (strength against tear), easiness in elongation of afilm, stiffness of a film, etc., at the same time, and the above film isstill unsatisfactory for these requirements.

The present inventors have made a further study to improve the film onthese points and arrived at an invention of a film of which the functionis improved by imparting individual layers with divided functionsseparately and synergistically and arranging the layersthree-dimensionally. For example, the film of the invention isremarkably much more improved in stretchability (particularly resistanceto bubble puncture) than that of the above prior application, excellentin strength against breach under a variety of film use conditions andpractically usable even though it has a small thickness.

That is, the present inventors have arrived at the present invention ofa novel film, a composite film, which can simultaneously overcome theabove-described defects of a variety of films and is most suitable for avariety of packaging methods by arranging specific layers and treatingthe film under specific conditions.

PREFERRED EMBODIMENTS OF THE INVENTION

The present invention has a characteristic feature in that the compositefilm has a layer containing a specific mixed composition.components,that other specific layers are further combined and that at least onelayer is highly stretched, preferably highly cold-stretched, whereby thestretch orientation effective for the unprecedented use of the presentinvention and other excellent properties which will follow are exhibitedby a synergistic effect of said mixed composition.components and thelayers of other resins.

The film of the present invention finds a wide range of use, that is, itcan be used as a household wrap film and as a film for other variouswrapping methods. Among these, it has excellent properties as a shrinkfilm as described above. In particular, it can be produced as a filmwhich is excellent in optical properties, strength, heat-sealability(surface sealability, fused sealability and hot tack properties),elongation and stress relaxation, and is also excellent inlow-temperature shrinkability and shrink response (speed). It canfurther meet the use for stretch-shrink wrapping and complete stretchwrapping.

FIRST ASPECT OF THE INVENTION

The first aspect of the present invention is directed to ahigh-strength, multi-layered film excellent in heat resistance, shrinkproperties, stretchability and sealability, which comprises at leastfive layers comprising surface layers (S layers) composed mainly of atleast one polymer selected from (A), (B), crystalline. 1.2 polybutadieneand soft ethylene-based copolymer ionomer resins, and, inner layers,which comprises at least one base layer (SBC layer) mainly containing amixed composition selected from (A)+(B)+(C), (A)+(B) and (B)+(C), atleast one core layer (H layer) mainly containing polymers selected from(C), and at least one auxiliary layer (R layer: provided that R layercontains a resin different from that selected for the S layer when Rlayer is adjacent to S layer) mainly containing at least One polymerselected from (A) and (B),

said (A) being at least one copolymer selected from low-densitypolyethylenes, copolymers of ethylene with at least one monomer selectedfrom vinyl ester monomers, aliphatic unsaturated monocarboxylic acidsand alkylesters of said monocarboxylic acids, and derivatives thereof,

said (B) being at least one soft thermoplastic elastomer having a Vicatsoftening point of 80° C. or lower,

said (C) being selected from a crystalline polypropylene, a crystallinepolybutene-1 and a crystalline poly-4-methylpentene-1 or a mixturethereof.

Preferred embodiments of the present invention are as follows.

A film in which the low-density polyethylene as component (A) is alinear low-density polyethylene (including utra-low-densitypolyethylene) obtained by copolymerizing ethylene and at least oneα-olefin selected from C₃ -C₁₂ α-olefins.

A film in which the low-density polyethylene as component (A) has aVicat softening point of 80° C. or higher.

A film in which the low-density polyethylene as component (A) is acopolymer obtained by copolymerizing ethylene and at least one α-olefinselected from C₆ -C₁₂ α-olefins.

A film in which component (A) is an ethylenevinyl acetate copolymer.

A film in which component (B) is at least one soft elastomer selectedfrom an ethylene-α-olefin copolymer, a copolymer from mutually differentα-olefins, a butyl rubber-based copolymer, a 1,2-polybutadiene-basedpolymer, a styrene-conjugated diene-based derivative copolymer and an atleast partially hydrogenated polymer obtained by a hydrogenating astyrene-conjugated diene-based derivative copolymer.

A film in which the soft elastomer as component (B) is anethylene-α-olefin copolymer containing 95 to 5 mol % of a contentderived from ethylene and a content derived from at least one α-olefinselected from C₃ -C₁₂ α-olefins.

A film in which the ethylene-α-olefin copolymer as component (B) has amelt index of 0.1 to 10 and a density of not more than 0.905 g/cm³.

A film in which the mixed composition in a base layer (SBC layer) has acomposition ratio by weight of 0.90≧B/(A+B)≧0.05, 0.90≧B/(B+C)≧0.30 or0.90≧B/(A+B)≧0.05 and 2.0≧C/(A+B)≧0.05.

A film in which the surface layer (S layer) mainly contains at least onepolymer selected from linear low density polyethylenes (includingultra-low-density polyethylenes) and an ethylene-vinyl acetate copolymerselected from component A.

A film in which the surface layer (S layer) is a soft thermoplasticelastomer having a Vicat softening point of 80° C. or lower selectedfrom component (B).

A film in which the auxiliary layer (R layer) is mainly composed of atleast one ethylene-α-olefin copolymer soft elastomer selected fromcomponent (B) and having a melt index of 0.1 to 10, a density of 0.905to 0.870 g/cm³ and an ethylene content of 95 to 85 mol % or at least onelinear low-density polyethylene (including ultra-low-densitypolyethylenes) selected from component (A) and having a melt index of0.1 to 10, a density of 0.905 to 0.935 g/cm³ and an ethylene content of99 to 90 mol %.

A film in which R layer is placed adjacent to S layer. In this case, Rlayer is an ethylene-α-olefin copolymer selected from component (A) andhaving a density of 0.905 to 0.935 g/cm³, and the Vicat softening pointof this resin is 1.05 times or more the Vicat softening point of a resinof the surface layer (S layer).

A film in which the base layer (SBC layer) is composed mainly of a mixedcomposition (A)+(B)+(C).

A film in which the core layer (H layer) is composed mainly ofcrystalline polypropylene and crystalline polybutene-1 from component(C).

A film having a seven-layer structure of S/R/H/SBC/H/R/S.

A film in which, based on the total thickness, the thickness of the baselayer (SBC layer) is 20 to 80%, that of the surface layer (S layer) is 5to 40%, that of the core layer (H layer) is 5 to 50% and that of theauxiliary layer (R layer) is 10 to 70%.

A film in which a 100% elongation stress of multi-layered film is of 100to 800 g/cm width on the average (of width and length directions).

A film in which multi-layered film is treated with energy beam and inwhich at least one layer has a boiling xylene-insoluble gel of 0 to 70%by weight and a melt index of 1.0 or less.

Another aspect of the present invention is directed to a process forproducing a highly stretched multi-layered film, which comprisesseparately melt-kneading resins which are to constitute at least fivelayers comprising surface layers (S layers) composed mainly of at leastone polymer selected from (A), (B), crystalline 1,2-polybutadiene and asoft ethylene-based copolymer ionomer resin, and, inner layers whichcomprises at least one base layer (SBC layer) mainly containing a mixedcomposition selected from (A)+(B)+(C), (A)+(B) and (B)+(C), at least onecore layer (H layer) mainly containing polymers selected from (C), andat least one auxiliary layer (R layer: provided that R layer comprises aresin different from that selected for S layer when R layer is adjacentto S layer) mainly containing at least one polymer selected from (A) and(B),

said (A) being at least one copolymer selected from low-densitypolyethylenes, copolymers of ethylene with at least one monomer selectedfrom vinyl ester monomers, aliphatic unsaturated monocarboxylic acidsand alkylesters of said monocarboxylic acids and derivatives thereof.

said (B) being a soft thermoplastic elastomer having a Vicat softeningpoint of 80° C. or lower,

said (C) being any one of a crystalline polypropylene, a crystallinepolybutene-1 and a crystalline poly-4-methylpentene-1 or a mixturethereof, extruding the resins through a multi-layer die, rapidly coolingand solidifying the extrudate by means of a liquid cooling medium toprepare a tubular or flat master roll, optionally heating it to atemperature of not more than a temperature of 120° C. and stretching itat a stretching temperature in the range of 30° to 110° C., and at anarea stretch ratio of 4 times to 30 times. Preferred embodiments thereofare as follows.

A process in which the stretching temperature is not higher than thecrystal melting point of a polymer which mainly compose at least onelayer constituting other layers than the core layer (H layer).

A process in which the orientation is modified by shrinking thepost-stretched raw film at 40° to 90° C. by at least 5 to 80% (area).

A process in which the rapidly cooled and solidified raw film isirradiated with high-energy beam having an energy of 100 KV to 1 MV at aradiation dose of 1 to 10 megarad, and then stretched.

The present invention will be described in detail hereinafter.

Component A

As component (A), a polymer having an intermediate degree between hardand soft and relatively low crystallinity (crystallinity of 20 to 60%,preferably 30 to 55% by an X-ray method) is mainly selected in view ofstretchability and physical properties (softness and strength). Thecomponent A includes an ethylene-based copolymer group (former) such aslow-density polyethylenes (preferably including ethylene-α-olefincopolymers such as linear low-density polyethylenes (LLDPE) andultra-low-density polyethylenes (VLDPE)) and a polar functionalgroup-containing group (latter) such as copolymers of ethylene with atleast one monomer selected from vinyl ester monomers, aliphaticunsaturated monocarboxylic acids and alkyl esters of said monocarboxylicacids, and derivatives thereof.

The latter group preferably includes an ethylene-vinyl acetate copolymer(EVA), an ethylene-ethyl acrylate copolymer (EEA), an ethylene-methylmethacrylate copolymer (EMMa), an ethylene-acrylic acid copolymer (EAA),an ethylene-methacrylic acid copolymer (EMA), an ethylene copolymer withan alkyl ester of an unsaturated monocarboxylic acid in which the alkylgroup of the alcohol component has 2 to 12 carbon atoms, preferably 2 to8 carbon atoms (e.g., propyl, butyl, hexyl and octyl), a terpolymerformed from at least two monomers above and a polymer (ionomer resin) ofwhich at least part has a saponified carboxyl group and at least part isconverted to an ionomer. The content derived from monomer(s) other thanethylene in these copolymers is preferably 1.5 to 12 mol %, morepreferably 2 to 10 mol %. When this content is 1.5 mol % or more, theresultant film is excellent in sealability, flexibility, transparencyand various strength properties. When this content exceeds 12 mol %, theextrusion processability, the mixability with other components and theheat resistance are inferior, or the use of component (A) as a surfacelayer (outer layer) sometimes causes blocking of the surfaces, which isa problem in handling. The melt index (ASTM: D1238 (E conditions): to bereferred to as MI hereinafter) of the resins, when used directly as amaterial, is generally 0.2 to 10, preferably 0.3 to 5. When it is lessthan 0.2, there is a problem on mixability of the materials andextrusion properties. When it exceeds 10, an interlayer disorder islikely to be caused in multi-layer extrusion. Further, there is a casewhen the strength as the base layer (SBC layer) is insufficient. Forexample, undesirably, there is a bad phenomenon that bubbles are likelyto break in stretching. Of the above, preferred for use as one componentin the base layer (SBC layer) is EVA, and the vinyl acetate (VAc)content thereof is preferably 3 to 8 mol %, more preferably 3 to 7 mol%.

Among the former polyethylene group, the linear low-density polyethylene(LLDPE) as a preferred example refers to a substantially linear, ornearly linear low density ethylene obtained by an intermediate-, low- oroptionally high-pressure method, which is obtained by copolymerizingethylene with not more than 9 mol %, preferably approximately 1.5 to 8mol % of at least one olefin selected from C₃ -C₁₂ α-olefins such aspropylene, butene, pentene, hexene, heptene, octene and4-methyl-1-pentene. MI of these LLDPEs (including VLDPE) is generally0.2 to 15, preferably 0.2 to 10 for the same reasons as those describedconcerning the above latter group. Further, the density is generally inthe range of 0.890 to 0.935 g/cm³. More preferred ultra-low-densitypolyethylene (VLDPE) refers to polyethylene which has the above factorsand has a relatively high copolymerization ratio (provided that thispolyethylene has a short-chain branch as the above comonomer but has anearly linear region of which the long-chain branch content issubstantially small or absent) and which generally has a density of0.890 to 0.905 g/cm³ (including 0.905 g/cm³) and a crystallinity ofapproximately 20 to 35%.

The usual linear low-density polyethylene portion other than the aboveVLDPE has a density of 0.905 to 0.935 g/cm³, preferably 0.910 to 0.935g/cm³. These resins has a VSP (to be described later) of 80° C. orhigher, preferably not less than 85° C. Alpha-olefin having 5 to 12carbon atoms are preferred as a comonomer. These polyolefins have acrystal melting point (mp) of not less than 108° C. to not more than125° C. at a main peak or a high-temperature side peak in the case ofmultipeaks (2 or 3) when measured by a DSC method (measured at a scanspeed of 10° C./minute), and can be distinguished from those having acrystal melting point of 100° to 108° C., having a long-chain branchedlow density polyethylene of 0.915 to 0.927 g/cm³ which are generallyproduced by high pressure method.

More preferred a mixed composition containing at least one copolymerselected from a copolymer group (Af) of the above EVA, EEA, EAA, EMMA,EMA and ethylene copolymer with said ester of which the alcoholcomponent has 2 to 8 carbon atoms and least one selected from acopolymer group (Al) of the above LLDPEs, VLDPEs and anethylene-α-olefin copolymer. In this case, the mixing ratio ispreferably 0.10≦Al/(Af+Al)≦0.9, more preferably 0.30≦Al/(Af+Al)≦0.70.Graft-modified resins (so-called modified resins) obtained by modifyingthe above resins with a carboxylic group-containing monomer may be used.

Component (B)

The soft thermoplastic elastomer having a Vicat softening point [ASTMD1525 (value under a load of 1 kg), to be referred to VSP] of 80° C. orlower is at least one polymer selected from an α-olefin elastomer, i.e.,a copolymer obtained from mutually different at least two α-olefins(carbon number, C₃ -C₁₂), a copolymer obtained from ethylene and anα-olefin having 3 to 12 carbon atoms, butyl rubber type elastomer,styrene-conjugated double bond diene derivative block copolymerelastomer, a copolymer prepared by hydrogenating at least part of aportion derived from the conjugated double bond polymer of saidelastomer and thermoplastic polyurethane. Graft-modified resins from theabove resins (treated in the same manner as above) may be used.

Of these, preferred are α-olefin elastomer, i.e., a copolymer ofα-olefins and a thermoplastic elastomer formed of a copolymer ofethylene and α-olefin. The former refers to a copolymer obtained from acombination of at least two different α-olefins (C₃ to C₁₂), and thelatter refers to a copolymer obtained from ethylene and at least oneselected from α-olefins having 3 to 12 carbon atoms. Further, thesecopolymers may have a content derived from a small amount of hydrocarbonhaving a polyene structure such as dicyclopentadiene, 1,4-hexadiene,ethylidene-norbornene, derivatives of these and other component. Theα-olefin includes propylene, butene-1, hexene-1, heptene-1,4-methylpentene-1 and octene-1. The former includes a copolymer frompropylene and butene-1, a copolymer from propylene and4-methyl-pentene-1 and a copolymer from butene-1 and 4-methylpentene-1.In the latter case, the α-olefin preferably includes propylene andbutene-1. The ethylene content in the copolymer is 5 to 95 mol %,preferably 40 to 93 mol %, more preferably 65 to 90 mol %. It is furtherpreferably 75 to 85 mol %.

These α-olefin elastomer copolymers generally have a density of 0.870 to0.905 g/cm³, preferably 0.880 to 0.900 g/cm³, they preferably has aVicat softening point of not more than 75° C., more preferably not morethan 70° C., further preferably of not more than 60° C. The α-olefinelastomer copolymer includes those which are substantially amorphous ina rubbery zone and partially crystalline copolymers which have acrystallinity (measured by an X-ray method) of about 30%, preferably notmore than 20%, more preferably not more than 15%, further preferably notmore than 10%. The melting point of the crystal thereof by a DSC method(temperature elevation ratio of 10° C./minute) is generally preferablynot more than 125° C., more preferably not more than 110° C., furtherpreferably not more than 100° C. Preferred are a copolymer from ethyleneand propylene or butene-1, a copolymer from propylene and any one or amixture of butene-1 and 4-methylpentene-1, and a copolymer from thesemonomers and those including a small amount of a compound having a dienestructure. For example, preferred is a thermoplastic elastomer which isa random copolymer obtained by polymerization in the presence of acatalyst containing a vanadium compound and an organoaluminum compoundand having MI of 0.1 to 10 preferably 0.2 to 6. These copolymerspreferably have no block form unlike general unvulcanized rubber, causeno cold flow, have the form of pellets, and have plasticity sufficientto enable the extrusion processing of themselves alone into a film form.

Component (C)

The component (C) includes crystalline polypropylene,high-molecular-weight crystalline polybutene-1 and crystallinepoly-4-methylpentene-1 (to be respectively abbreviated as IPP, PB-1 andPMT-1 hereinafter) which are formed from a relatively hard (harder thanthe components (A) and (B)) and relatively highly crystalline. Each or amixture of these as component (C) has a Vicat softening point (specifiedalready) of not less than 80° C., preferably not less than 90° C., morepreferably not less than 100° C.

IPP included in the component (C) refers to generally commerciallyavailable crystalline PP having high isotacticity. Preferred are ahomopolymer of propylene and copolymer from propylene and not more than7 mol % of ethylene, butene-1 or other α-olefin. IPP is not limited tothe above. IPP may be another copolymer which is obtained from α-olefins(for example, a copolymer obtained by arbitrary combining propylene,butene-1, 4-methylpentene-1, etc., or obtained from these and a smallamount of ethylene, although PP shall not be limited to these) and whichsatisfies the above properties. IPP may be a mixture of the abovecopolymers. The melt flow index [measured by ASTM: D1238 (L conditions),to be abbreviated as MFI hereinafter] is 0.1 to 30, preferably 0.5 to20, more preferably 0.7 to 15. When MFI is less than the above, therearises a problem on the mixability in processing and the opticalproperties. When it is used in an amount exceeding the above, therearises a problem on the extrusion stability and the stability in asealing portion.

PB-1 is crystalline polymer having a butene-1 content of not less than93 mol % and it is also a high-molecular-weight polymer including acopolymer from another monomer (for example, ethylene, propylene andothers having at least 5 carbon atoms). Differing from liquid andwax-like polymers having a low molecular weight, for the same reasonsdescribed about the above IPP, polymers having a melt index of 0.2 to 10are preferred. Also preferred is a mixture of IPP and PB-1, either oneof these or a composition obtained by adding a hydrogenated hydrocarbonresin (preferably a hydrogenated hydrocarbon resin obtained fromconstituent monomers, at least one of which at least partially containsa cyclic portion) to one of these two or both. In addition to these, ahard polymer may be used if it has compatibility and dispersibility andmeets the object of the present invention.

PMT-1 may include crystalline copolymers having a 4-methylpentene-1content of at least 90 mol % and obtained from at least one otherα-olefin monomer. Further, the polymer and copolymers may be used in anymixing ratio. PMT-1 may contain the above IPP, PB-1 or other known resinin an amount of not more than 50 wt %. This amount is preferably notmore than 40 wt %, more preferably 30 wt %.

There may be used one obtained by adding to the above component (C) atleast one of an AS agent and P agent which will follow in an amountwhich will follow, or there may be used one obtained by allowing it tosupport additives such as anti-fogging agents and plasticizers whichwill follow.

SBC layer

The base layer (SBC layer) composed of a specific mixedcomposition.component in the film of the present invention comprises theabove components, and mainly contains (1) (A) and (B), (2) (B) and (C)or (3) (A), (B) and (C). The amount range of these is preferably

(1) 0.05≦B/(A+B)≦0.90,

(2) 0.30≦B/(B+C)≦0.90 or

(3) 0.05≦B/(A+B)≦0.90 and 0.05≦C/(A+B)≦2.0,

more preferably,

(1) 0.07≦B/(A+B)≦0.70

(2) 0.40≦B/(B+C)≦0.87 or

(3) 0.07≦B/(A+B)≦0.70 and 0.07≦C/(A+B)≦1.0,

further preferably

(1) 0.10≦B/(A+B)≦0.50

(2) 0.50≦B/(B+C)≦0.85 or

(3) 0.10≦B/(A+B)≦0.50 and 0.10≦C/(A+B)≦1.0.

When the amount of the soft component (B) is small, mixtures in any caseof (1), (2) and (3) hardly exhibit any synergistic effect, and theproperties decrease. For example, the resultant film is inferior instrength, optical properties, low-temperature properties, flexibility,sealability and stretchability. When it is too large, the resultant filmis too soft, and tends to be poor in heat resistance, sealability andoptical properties. Further, when the amount of the component (B) isselected from the preferable range, or from the further preferablerange, the synergistic effect of the mixture increases in any case of(1), (2) and (3), and the various properties are more improved. Forexample, the film strength, optical properties, low-temperatureproperties, flexibility, sealability and stretchability are improvedfurther.

Of the above combinations, particularly preferred is the combination (3)mainly containing (A), (B) and (C). Further preferred is a combinationof (A), (B) and (C) to which 1 to 10% by weight of at least one additiveselected from anti-fogging agents and plasticizers is added, and furtherpreferred is a mixture of this with 1 to 30% by weight of at least oneresin (to be described later) which is to support said additives. Thistendency similarly appears in the other cases of (1) [A+B] and (2)[B+C]. The component (C) improves the tensile, impact strength, heatresistance, extrusion.stretchability, elastic modulus and heat-sealablerange of the mixed composition synergistically with other components,and particularly has a great effect on the heat resistance,extrusion.stretchability, elastic modulus and heat-sealable range. Whenthe mixed amount is small, the effect is lower on the improvement, forexample, of film processability or heat-sealable range and strength. Theexpected value of heat resistance also decreases. When it is too large,the effect is poor in extrusion moldability, transparency, flexibilityand impact resistance. Therefore, it is preferably in the above range.The component (A) preferably comprises a specific ethylene-basedcopolymer among the aforedescribed ones, and in some cases, it ispreferred to use the component (A) as a main component among the thosecomponents (A), (B) and (C).

A mixture of the components (A) and (C) alone is generally poor inmixability and compatibility, and the above synergistic effect cannot beexpected. However, when the component (B) is added, these defects can beremarkably overcome.

The reason therefor is considered to be that the above is due to acomplex synergistic effect including a subtle interaction between theproperties derived from a structure relating to ethylene and a polarfunctional group (in a preferable case) contained in the component (A)and other components, or the crystal structure of the mixture and thedispersion state of the mixture, and an effect of the aforementionedpost treatment.

For example, when the component (A) is main, it is considered that thereis a state of a synergistic effect in which, when the above componentsare dry-blended in the form of pellets, melt-kneaded and extruded with ahighly efficient extruder to form a raw film, the component (B)intricately disperses itself or reacts inside or near the component (C)dispersed in the component (A).

The form of these molded articles differs depending upon moldingconditions when these are processed into a film-shaped molded articleand imparted with flow orientation.

For example, when a film is formed from the above mixture by extrudingthe mixture through a film- or sheet-forming die having a small slit(e.g. 1.5 mm) at a relatively high temperature of 230° to 260° C.optionally under a predetermined draw ratio, rapidly cooling theextrudate and processing it into a film, the following is consideredalthough it depends on the kind and amount of the component (C). Whenthe mixture contains 20% by weight of PP, some portions of the component(C), PP, have its dispersed particles in a fibrous form oriented in theflowing direction in the main component (A), and the resultant film isstructured as if the film were reinforced with a glass fiber. As aresult, the film may exhibit very improved properties such as improvedstrength. In some cases, further improved properties are exhibited byadding processing such as energy beam processing, chemical treatment andion injection after the above treatment. This is not necessarilyessential.

In the case of (2) (B)+(C), the (B) thermoplastic elastomer particularlypreferred is an amorphous or partial-low-crystallinity copolymer havingan ethylene content of 65 to 95 mol %, preferably 75 to 93 mol %. Thisincludes a random copolymer obtained from propylene and butene-1, and issupplied in the form of pellets.

Further, the base layer (SBC layer) may contain other known resin if itcontains at least 50% by weight, preferably 80% by weight or more of thepolymer mixture of the above (1), (2) and (3) and if the other resindoes not impair various properties of the film.

Furthermore, preferably the base layer (SBC layer) of the specialmulti-layered film of the present invention after extruded in the formof multi-layer together with other resins is subjected to activationtreatment with high-energy beams such as electron beam (β-ray), γ-rayand ultraviolet ray having an energy of 100 KV-1 MV to treat the alllayers or optional layer(s), or to treat gradiently it in the thicknessdirection or is modified by allowing a selective crosslinking reactionto take place in continuous phase or dispersion phase of the base layer(SBC layer) prepared by mixing other resins with the base resin todisperse the other resins in the form of particles, plates, fibers ornet work. These treatments result in remarkable improvements of strength(especially tear strength), heat resistance, and stretchability. Thedegree of the "crosslinking" is such that boiling xylene-insoluble gelcontent is 0-50% by weight and MI is 1.0 or less, preferably the gelcontent is 0.1-40% by weight and MI is 0.5 or less, more preferably thegel content 0.5-30% by weight and MI is 0.1 or less, further preferablythe gel content is 1-25% by weight and MI is 0.1 or less and mostpreferably the gel content is 1-20% by weight and MI is 0.1 or less as awhole of the specified layers or preferably in the unit of at least 0.3μm in the thickness direction in the case of gradient treatment in thelayer and in terms of single material as a whole of the dispersion layerin the case of dispersion state.

When the insoluble gel content is larger than the above amount, themolded article shows decrease in elongation, strength and deterioration.In particular, a film formed therefrom causes the problems that theheat-sealability deteriorates, for example, it cannot be sealed or itcannot be cut with a heating wire, that it is liable to break, and thatthe degree of stretchability imparted by post treatment is small.Therefore, the above range is preferred. When the undissolved gelcontent is set in the preferable range or in the more preferred range,the film is more improved in the property balance among sealability,heat resistance, stretchability, and the like.

The insoluble gel content can be obtained from calibration curve easilyprepared from dosage by treatment of single material.

In the thickness structure, the percentage of the base layer (SBC layer)based on the total thickness of the film is preferably 20 to 80%, morepreferably 30 to 70%, further preferably 40 to 70%. The lower limit ofthe above range is the percentage required for producing the synergisticeffect of the present invention by particularly stably (without breachof the film by puncture and surging) achieving the cold stretching ofother layers as well, which could not be successfully cold-stretched inthemselves, with the cold stretching force of the base layer (SBClayer). This is also the thickness required for producing theabove-described various properties which the composition of the baselayer imparts. A similar effect is also obtained in a high-temperaturestretching zone. The optimum percentage thereof can be determineddepending upon the purpose of the film. For example, when other layersinclude a composition layer which can be hardly imparted with coldstretching, the lower limit of the thickness of the base layer isrelatively higher. When a composition layer which can be easily impartedwith it is included, the layer percentage level may be lower if theprocessability alone is considered. However, in order to take advantageof the properties of the base layer formed from said composition afterstretching other than the processability (i.e., cold stretching force)of the base layer, it can be determined after a balance between thesetwo is considered. The upper limit of the above range is the percentageto be determined depending upon the effect of the other layer to beused, and it can be determined depending upon a purpose and as required.

H layer.

The core layer (H layer) composed of the component (C) as other layer ofthe present invention has a higher elastic modulus than any other layer,and it imparts the entire film with rigidity, imparts the entire filmwith dimensional stability, and imparts the film with heat resistancerepresented by VSP, melting point. It is composed mainly of a singlepolymer or polymer mixture selected from the aforedescribed crystallinepolypropylene (IPP), crystalline polybutene-1 (PB-1), crystallinepoly-4-methyl.pentene-1 (PMT-1) and other α-olefin copolymers, and it ispreferably a polymer mixture. In addition to the above polymers, thecore layer may contain not more than 50% by weight, preferably not morethan 40% by weight, more preferably not more than 30% by weight of thepolymer(s) described concerning the other layers of the presentinvention or other known polymer(s). To be more specific, these "other"polymers include a resin or resin mixture used in the above base layer(SBC layer), resins or petroleum resins used in the surface layer (Slayer) and auxiliary layer (R layer) which will be described later, andother known resins. These may be [IPP+PB-1+petroleum resin],[IPP+component (A)] and [IPP+component (B)]. The core layer may beimparted with heat resistance by using a highly crosslinkable resin andcrosslinking it preferentially over other layers. In this case, it isadvantageous to constitute the composition of the core layer (H layer)so as to have higher heat resistance than any other layer. The "heatresistance" refers to the properties of the resin per se or the resinmixture and a value expressed as a synergistic effect of the other-layerin the use to be described later, particularly when the sealability ismeasured. The multi-layered film of the present invention has thecontradictory properties, heat resistance, low-temperature shrinkingproperties and stretchability. When the core layer is present as a layerobtained by a high-temperature (higher than melting point) stretchingmethod other than the preferred process of the present invention, ageneral low-stretch ratio stretching method or an unstretched method,the object of the present invention, of course, cannot be achieved. Thepercentage of the thickness of the H layer based on the total thicknessof the film is preferably 5 to 60%, more preferably 5 to 40%, furtherpreferably 5 to 30%. In particular, when the film is used for stretchwrapping, it is 5 to 20%. The lower limit is set for a reason that thecore layer (H layer) takes part in exhibiting the above synergisticeffect. The upper limit is set for reasons that the synergistic effectwith the other layers such as the base layer (SBC layer), the surfacelayer (S layer) and the auxiliary layer (R layer) is not exhibited anyfurther and that the processability is decreased even if the amountexceeds it. For the layer constitution meeting a purpose, it issufficient to set the percentage of the thickness of the core layer inthe above range. In addition, the lower limit of the thickness ispreferably 0.5 μm.

S layer

The surface layer (S layer) is composed mainly of at least one polymerselected from the component (A), the component (B) and other resin.These copolymers are selected from those specified as the component (A)such as linear low-density polyethylenes (LLDPEs including VLDPEs), anethylene-vinyl acetate copolymer (EVA), an ethylene-acrylic acidcopolymer (EAA), an ethylene-acrylic acid ester copolymer, anethylene-methacrylic acid copolymer (EMA), an ethylene-methacrylic acidester copolymer, a copolymer of ethylene with an alkyl ester of saidunsaturated carboxylic acid in which the alkyl group of the alcoholcomponent has 2 to 12 carbon atoms, preferably 2 to 8 carbon atoms(e.g., propyl, butyl, pentyl, hexyl, heptyl and octyl) and amulti-element copolymer formed therefrom, an ethylene-α-olefin copolymerincluded in the component (B) (preferably an ethylene-butene-1 randomthermoplastic elastomer), crystalline 1,2-polybutadiene, and a resin(Io) obtained by saponifying at least part of ethylene-acrylic acidester or ethylene-methacrylic acid ester and further crosslinking atleast part thereof.

LLDPEs (excluding VLDPEs, which will be described later) preferably hasMI of 0.2 to 10 and a density of 0.905 to 0.935 g/cm³, more preferablyhas MI of 0.2 to 8 and a density of 0.910 to 0.925 g/cm³, furtherpreferably has MI of 0.2 to 6. The lower limit of the MI is set for areason that the extrusion to form a film has a limit. The upper limit isset for reasons that the use of such a material for the surface layer (Slayer) makes the cold stretchability of the above base layer (SBC layer)unstable, that the seal strength of the sealed portion of the film isinsufficient, that the film strength is insufficient and that the filmstretchability is insufficient. The upper limit is also set because of atendency toward instability of stretchability, a decrease inlow-temperature sealability of a cold-stretched film, bleedingproperties of additives, a decrease in optical properties, andparticularly extreme deterioration of optical properties after the filmis shrunk (e.g., haze value and gloss). The following has been found; Inthe above range, the above processability and the various properties arenot deteriorated, and the various properties of the multi-layered film,particularly the base layer (SBC layer) are not deteriorated. Incontrast, due to the synergistic effect with other layers, these factorsare remarkably improved. In properties in particular, the variousstrength properties, the sealability and the resistance to an oil at ahigh temperature are remarkably improved. It is preferred to use onehaving a crystal melting point (mp) of 110° to 125° C. as a main peakvalue or a high-temperature side peak value in case of a plurality ofpeaks, measured by a DSC method (temperature elevation rate 10°C./minute). It is also preferred to use one obtained from octene-1,4-methylpentene-1 and hexene-1 as a comonomer in view of filmformability and tear strength. Further, LLDPE which is a main componentmay be used in combination with ones disclosed in the presentspecification or other known polymers if these do not impair the aboveproperties. The limit of the amount of these other components is notmore than 50% by weight, preferably not more than 40% by weight, morepreferably not more than 30% by weight.

In case of preferred ultra-low-density polyethylene (VLDPE), itgenerally has a melt index of 0.2 to 15, preferably has a melt index of0.2 to 10. The upper and lower limits above are set for the same reasonsas those described concerning LLDPE. The density is preferably 0.880 to0.910 g/cm³, more preferably 0.890 to 0.905 g/cm³. The upper limit ofthe density is set because of flexibility, a decrease in an elongationstress and widening of the lower limit of the heat-sealable temperaturein the film grade for a more stretching use. The lower limit is set dueto the film strength (tear strength) and excess sticky nature on thefilm surface. VLDPE may be used in combination with other resins in thesame manner as in the case of the above LLDPE. The same can be appliedto other soft elastomers than those mentioned above. The crystallinityof VLDPE (by an X-ray method) is preferably 10 to 40%, preferablyapproximately 15 to 35%.

In the ethylene-vinyl acetate copolymer (EVA), the vinyl acetate group(VAc) content is 3 to 10 mol %, preferably 3 to 7.5 mol %, morepreferably 3.5 to 6 mol %. MI is preferably 0.2 to 5, more preferably0.5 to 3, further preferably 0.5 to 2.0. This description can apply tothe other copolymers obtained from aliphatic unsaturated monomers. Thesurface layer may be formed from a copolymer or monomer having acarboxylic acid group or a resin blend, and the surface layer may besubjected to ionomerization treatment (e.g., chemical treatment andphysical treatment such as ion injection, to add alkali metal oralkaline earth metal), crosslinking treatment or other chemical reactiontreatment such as grafting. These treatments may be carried out with anangle in the thickness direction of the layer.

The ethylene-α-olefin copolymer is preferably a random thermoplasticcopolymer elastomer obtained from ethylene and at least one of butene-1,4-methylpentene-1, hexene and octene. This elastomer has MI of 0.5 to10.

The crystalline 1,2-polybutadiene copolymer is thermoplastic, and has acrystallinity of 10 to 35% and MFI (the aforedescribed ASTM method, Cconditions) of 1 to 10. Plasticized PVC may be used case by case.

Of the above, preferred is the case in which the surface layer iscomposed mainly of EVA. Further, a mixture of the above resins for thesurface layer (S layer) may be used. Further, the material for thesurface layer may contain other resins described in the presentinvention and other known resins in such an amount that they do notimpair the object of this layer, low-temperature heat-sealability,bleeding properties of additives, optical properties (particularlyimprovement in haze and gloss values) and the characteristic in that thedeterioration of the optical properties after the film is allowed toshrink is prevented by a synergistic effect with the other layers. Theamount thereof is not more than 50% by weight, preferably not more than40% by weight, more preferably not more than 30% by weight.

The percentage of the thickness of the surface layer (S layer) based onthe total thickness of the film is preferably 5 to 40%, more preferably10 to 40%, more preferably 15 to 30%. Further, the total thickness ispreferably 0.5 to 25μ, more preferably 1 to 20μ. The above "lower limit"is the minimum thickness required for the surface layer (S layer)exhibiting its effect synergistically with the other layers. The upperlimit is the limit required to obtain the processability and theproperties of the other layers.

R layer

The auxiliary layer (R layer) is described hereinafter, which improvesthe tear strength synergistically with the other layers and controls thebleeding of additives. The R layer characteristically refers to at leastone layer composed mainly of at least one polymer selected from theaforedescribed components (A) and (B). However, when R layer is placedadjacent to the above S layer, R layer is composed of a resin which isdifferent from the resin selected from S layer (in copolymerizationratio, graft treatment, MI, crystallinity, density, monomers). The resinselected from the preferred component (A) to constitute this layerincludes linear low-density polyethylene (LLDPE) or ultra-low-densitypolyethylene (VLDPE) included therein, an ethylene-vinyl acetatecopolymer (EVA), an ethylene-acrylic acid copolymer (EAA), anethylene-acrylic acid ester copolymer (EEA) and an ionomer resin. Inthese copolymers, the content derived from monomers other than ethyleneis preferably 2 to 12 mol %, preferably 2.5 to 10 mol %. When thiscontent is less than 2 mol %, the film tends to show a decrease inflexibility, stretching properties, resistance to tear andstretchability. When it exceeds 12 mol %, the extrusion moldability,stretchability, resistance to tear tend to decrease.

The above copolymers generally have MI of 0.2 to 15, preferably 0.2 to10. When MI is less than the lower limit, the extrusion moldability andthe mixability in use as a mixture decrease. When it exceeds the upperlimit, the extrusion moldability (in particular, interlayer disorder)and the tear resistance tend to decrease. Of the above, preferred isLLDPE (density 0.905 to 0.935 g/cm³). More preferred is one obtainedfrom ethylene and α-olefin having 5 to 12 carbon atoms. When R layer isplaced adjacent to S layer, preferred is a resin, having a VSP which isat least 1.05 times the VSP of the resin of S layer, and more preferredis an ethylene-α-olefin copolymer selected from the component (A) andhaving a density of 0.905 to 0.935 g/cm³. When an ethylene-α-olefincopolymer is selected for the surface layer (S layer), there is selecteda resin having VSP which is 1.05 times or more higher than VSP of theresin of said surface layer. In this case, the strength in a sealingportion and the low-temperature sealability tend to be more improved.

In place of the above ethylene-based copolymer, there may be used acopolymer (B) composed mainly of other α-olefin and ethylene-α-olefincopolymers other than the above. In this case, the abovecopolymerization ratio and the limitation of MI can also apply.

Of the above, preferred is LLDPE (including VLDPE) having a density of0.870 to 0.915 g/cm³, preferably 0.880 to 0.910 g/cm³ or otherethylene-α-olefin copolymer. And, it is advantageous to use a copolymerobtained from an α-olefin having 4 to 12 carbon atoms, preferably 5 to10 carbon atoms (e.g., 4-methylpentene-1, hexene and octene) in view ofimprovement particularly in tear resistance among the above describedproperties. When stretchability of a film is regarded as important inaddition to the above, preferred is one having a density of 0.880 to0.905 g/cm³. The film is preferably provided with at least two R layers,and in this case, the number of other layer(s) between R layers ispreferably one, more preferably two and further preferably three.

The percentage of the total thickness of the R layer based on the totalthickness of the film is generally 5 to 45%, preferably 10 to 40% forboth a single or a multi-R layers. Further, the total thickness thereofis 0.5 to 15 μm, preferably approximately 1 to 10 μm.

Additives to layers

An additive may be incorporated into at least one of the surface layer(S layer), the base layer (SBC layer) and the auxiliary layer (R layer).The additive includes slip agents such as erucic amide, behenic amide,acid bisamide-based agents, oleic amide and stearic amide, liquid slipagents such as silicon-based agents and polyethylene glycol-basedagents, various solid resins, fine particles of crosslinked resins(average particle diameter 0.1 to 5 μm), inorganic fillers and others.These are used alone or in combination. The amount thereof is 0.1 to2.0% by weight, preferably 0.2 to 1.0% by weight. An anti-fogging agentmay be also used alone or in combination with the above slip agent. Theanti-fogging agent includes nonionic surfactants such as polyhydricalcohol esters of fatty acids, polyoxyethylene alkyl ether,polyoxyethylene alkyl phenyl ethers. For these, there is used at leastone of monoester of glycerin and either oleic acid or stearic acid,diglycerin monoglyceride of oleic acid or lauric acid, sorbitanmonolaurate, polyoxyethylene alkyl ether, polyoxyethylene sorbitan oleicacid ester, polyoxy.ethylenenonyl.phenyl ether, alkyl.alkylolamide,alkylalkylolamine, polyoxyethylene monooleate and others. The amountthereof for use in each of the layers is generally 0.3 to 5% by weight.

In addition, a small amount of mineral oil and a small amount of a knownplasticizer may be added to the above layers. The amount of each for useis preferably approximately 0.5 to 5% by weight. Further, a tackifier(to be referred to as P agent) may be added to the above as required.The tackifier includes alicyclic unsaturated hydrocarbon-based resins(hydrogenated cyclopentadiene resin, a hydrogenation resin from apetroleum resin containing a cyclic component as a C₉ fraction, etc.),resins, esterified rosins, petroleum resins other then the above, andterpene resins. The amount thereof for use is preferably 0.5 to 7% byweight, more preferably 1 to 5% by weight. These additives can be addedto any layer(s) alone or in combination depending upon purposes. Thetotal amount thereof for use is nearly 0.5 to 15% by weight, preferably1 to 10% by weight.

When the above additives are incorporated into one or both of the baselayer (SBC layer) and R layer as internal layers, these produce afurther effect. In this case, these additives bleed out to the filmsurface through the surface layer (S layer) and produce their increasedeffect as compared with the case in which these are added to the surfacelayer (S layer) alone. Further, the bleed speed can be adjusted by thebase layer (SBC layer). Thus, there is produced a synergistic effect onretaining the persistence of the effect. Further, unexpectedly, aphenomenon of contamination on the film surface occurs to a particularlyless degree than that in the case of adding the additives to a singlelayer, the reason for which is not yet known.

Further, especially excellent synergistic effect can be exhibited whento the base layer (SBC layer) are added the P agent, at least one ofAPP, 1.2PB, EVA of high VAc content and others, and 1-30% by weight,more preferably 3-20% by weight, further preferably 5-15% by weight of acarrier resin (AS agent) which retains the above-mentioned anti-foggingagent and plasticizer and inhibits bleeding of these additives andamounts of the additives are freely balanced. That is, the anti-foggingagent and the plasticizer are effectively retained and total amount ofthese additives acts as a polymer plasticizer without bleeding most ofthese additives and they are stabilized. Further surprisingly, it hasbeen found that the addition of the carrier resin is effective forreduction of rubber elastic component by improvement of hysteresis curveof the whole film caused by impartment of an elasticity which is aviscoelastic property which has not been sufficiently attained. As aresult, the wrapping capability has been remarkably improved.

Further, it has been also made clear that the sticky nature on the filmsurface and the contamination of an article to be wrapped, which are ofserious problems in wrapping, are reduced. The above balanced amountsproduce interesting effects: It is made possible to satisfy both theplasticizing effect and the rigidity which are contradictory to eachother (even if the film thickness is decreased, e.g., to 5 to 10μ,surprisingly, the degree of easiness of wrapping increases). It alsosatisfies the film moldability, in particular, the cold stretchabilityto be stabilized (less puncture, etc). Specific heat treatment worksgood, and the elongation stress is easily decreased (that is, the filmis modified due to partial removal of orientation, and easilyelongated). A portion modified in stretch wrapping is againcold-stretched in the elongation direction, and the film strengthnonlinearly and easily increases with elongation (wrapping is madeeasier). This effect can be applied to the other layers. Resinsrecovered from all the layers may be incorporated into at least one of Slayer, R layer, H layer and the base layer in such an amount that doesnot exceed 30 wt %. It is preferred to incorporate it into the baselayer.

Layer arrangement of multi-layered film

Examples of the above compositions and the layer constitution aredescribed below, in which the base layer is SBC layer, the surface layeris S layer, the auxiliary layer is R layer and a heat resistance layeras the core layer is H layer. Other combinations are also possible, andthe present invention shall not be limited to the following examples.

(1) Five layers

S/SBC/H/R/S,

S/SBC/R/H/S,

S/R/SBC/H/S

(2) Six layers

i) S/SBC/H/SBC/R/S, S/SBC/H/R/SBC/S,

i) S/R/SBC/H/R/S, S/R/SBC/R/H/S,

iii) S/H/SBC/R/H/S, S/H/SBC/H/R/S,

(3) Seven layers

i) S/R/SBC/H/SBC/R/S, S/SBC/R/H/R/SBC/S, S/R/SBC/R/H/SBC/S,S/H/R/SBC/R/SBC/S, S/H/SBC/R/SBC/R/S

ii) S/H/R/SBC/R/H/S, S/R/H/SBC/H/R/S, S/R/SBC/H/R/H/S, S/R/H/SBC/R/H/S,S/SBC/H/R/H/R/S, S/SBC/R/H/R/H/S

iii) S/H/R/SBC/H/SBC/S, S/H/SBC/R/SBC/H/S, S/SBC/H/R/H/SBC/S,S/R/SBC/H/SBC/H/S, S/H/SBC/R/H/SBC/S, S/SBC/R/H/SBC/H/S,

(4) Eight layers

S/R/H/SBC/R/SBC/H/S,

S/R/H/SBC/H/SBC/R/S,

S/R/H/SBC/R/SBC/R/S,

S/H/SBC/R/SBC/R/SBC/S,

(5) Double

There is also included a film obtained by selecting arbitrary two filmsfrom the above combinations, stacking one on the other, and bondingthese two in a double state as they are or attaching the facing surfacesby blocking or sealing to form one sheet.

In the above combination, - - - /SBC/ - - - includes not only anembodiment containing one base layer (SBC layer) but also an embodimentin which at least two base layers (SBC layers) having mutually differentcompositions are laminated as - - - (SBC)₁ /(SBC)₂ - - - or a recoveredlayer is incorporated into the base layer (SBC layer). This is also thecase with the other layers other than the base layer. A particularlypreferable tendency is found when a layer having a relatively hightensile modulus, e.g., the core layer, is divided into two layers ormore and placed near the film surface layer (S layer). That is, althoughthe tensile modulus of the entire film remains unchanged in the abovecase, the flexural modulus of the film is greatly improved. When theso-constituted film having an extremely small thickness is for practicalwrapping, the wrapping suitability (handling properties and mechanicalsuitability) and the properties of the folded film for setting it aregreatly improved. Further, surprisingly, when the auxiliary layer (Rlayer) is similarly divided, there is produced an unexpected synergisticeffect that the resistance to tear is remarkably improved as comparedwith the case where it is present as a single layer. The principle ofthese is not known in detail. However, it is assumed that the effect ofdispersing the stress concentration in a tear point is advantageouslyproduced in the case where a specific layer is divided into two layersor more and these layers are placed as far as possible in the thicknessdirection with other layer(s) therebetween, than in the case where it ispresent as a single layer.

In addition to the above, layer(s) composed of other different resin(s),e.g., thin PVC layer(s) having a total thickness of 1 to 10μ, may beincorporated (particularly as a surface layer (S layer)), and thepresent invention shall not be limited to the above embodiments.

The entire thickness of the film of the present invention is generally 3to 50μ, preferably 5 to 30μ, more preferably 6 to 25μ. The film of thepresent invention remarkably produces excellent characteristics as astretch film for tray wrapping and no tray wrapping when it has anextremely small thickness of 5 to 20μ, preferably 6 to 15μ, morepreferably 6 to 11μ. However, the thickness of the film of the presentinvention shall not be limited to these. The lower limit of thethickness is the minimum at which the film can be stretched since thefilm specially has high strength, and the minimum at which the film cancompete with other conventional films, even if it is thinner than anyother film, since it has a higher strength over any conventional film.When the above thickness is smaller than the above lower limit, itcauses a problem in manufacturing and handling. The upper limit is setnaturally for a reason based on manufacturing and for a reason that ithas sufficient properties as compared with other films having a largerthickness. For example, surprisingly, while a general soft PVC stretchfilm has a practical thickness of 16μ, the film of the present inventionis superior in many ways in practical use even if the film of thepresent invention has a thickness, e.g., of 7 to 10μ.

The film of the present invention may be that which is nearlymonoaxially stretched lengthwise or widthwise according tocold-stretching as a preferred embodiment in addition to that which isbiaxially stretched. However, the film of the present invention ispreferably that which is first biaxially stretched and then allows thelengthwise or widthwise shifting of the orientation. Depending uponusage and use, the stretchability of the film can be controlled. Thispoint is not observed in any conventional films. Further, the film ofthe present invention is so formed that it can be imparted withelongation by freely changing its orientation (removing the orientation)by heat-treating it in a constrained state, in a freely shrunk state orin a monoaxially shrunk free state, and further, it can be againimparted with cold orientation depending upon the stretching degree inwrapping thereby to strengthen it in wrapping, whereby wrapping can beremarkably easily conducted. Among other numerous characteristics, thisis the most advantageous point of the present invention. This isachieved by an unconventional new technique and method. As describedabove, it is preferred to carry out the biaxially stretching first.

The film of the present invention has an optical properties [haze value(ASTM-D1003-52)] of not more than 3.0%, preferably 2.0%. For example, inRun No. 5 in Example 1, the haze value is 0.5%, or the film isremarkably superior. According to the present invention, the film can beprocessed without impairing the properties (a crystal form which issmall in an amount and fine) obtained by rapidly cooling thecomposition. That is, the film of the present invention can beparticularly transparent, since it can be stretched stably in a bubbleform at a temperature of not higher than the melting point, preferablynot higher than the softening point, of the composition used as a maincomponent.

The film of the present invention has a low-temperature shrinkability ofnot less than 15% at 80° C., and therefore, it can be effectively usedwhen an article which cannot be wrapped by a stretch method alone iswrapped. This point is not possible with any conventionalstretch-wrapping film.

The heat shrinkage is a specific value obtained by taking a square testpiece from film, drawing lines lengthwise and widthwise at apredetermined dimension, covering a powder such as a talc powder so thatthe test pieces does not adhere to its other portion or other substance,treating it with hot air having a predetermined temperature for 5minutes to allow it to shrink, then obtaining change ratios in bothdirections and calculating an average of the lengthwise change ratio andthe widthwise change ratio.

The present invention also has a characteristic feature in that therigidity of the film can be freely adjusted to a soft one to arelatively hard one by changing the constitution of the base layer (SBClayer), the constitution of the core layer (H layer) or the thicknessesor compositions of both.

Further, the film of the present invention has another characteristicfeature in that it has particularly high tensile strength. In thedirection in which the tensile strength is high, at an average in thedirections lengthwise and widthwise or in each of the directionslengthwise and widthwise, the film of the present invention has atensile break strength (the value and values to follow were all obtainedby the measurement according to the ASTMD 882-67 method) of at least 4kg/mm², preferably at least 5 kg/mm², more preferably at least 6 kg/mm².The film of the present invention also has a tensile break elongation,in the stretching direction (in the easily stretchable direction), at anaverage in both the directions, or preferably in the both directions, ofat least 150%, preferably at least 200%, more preferably at least 250%.

The above high tensile strength and great elongation means that the filmis tough and does not easily break, and are highly advantageous as afilm for protecting a wrapped article, and the thickness of the film canbe remarkably saved.

The film of the present invention further has a characteristic featurein that it is particularly excellent in tear strength (measuredaccording to ASTM D1922-67 at 50 to 100% of a full scale) in addition tothe above features. This value (as a film having a thickness of 10μ) isat least not less than 10 g, preferably not less than 15 g, morepreferably not less than 20 g. For example, the film obtained in Run No.11 in Example 3 has a tear strength of 62 g, while the film in Run No.(1) as a comparative example in Example 3 has a low tear strength of 3g, which has a similar layer structure but has no auxiliary layer (Rlayer). From these results, it is clear that Example of the presentinvention produces a remarkably excellent effect.

The film of the present invention is at the level at which the tensilebreak strength (average of those lengthwise and widthwise) is 10.8kg/mm² and the tensile break elongation is 380% as will be describedlater (in Example 1, Run No. 7). In general, when the strength isimproved by orientation according to a conventional method, the tensilebreak elongation tends to extremely decrease. For example, acommercially available, fully crosslinked (insoluble gel in boilingxylene 67% by weight) film composed of low-density polyethylene alone,described in Example 1, Comparative (b), has a tensile break strength of6.9 kg/mm² and a tensile break elongation of 110%, which values are low.As a result, this film is too easily broken to be used for stretchwrapping. The film of the present invention has the following propertiesfor a stretch film easily stretchable under a small load, one of theimportant uses of the present invention.

The stretchability is the most important factor for conducting stretchwrapping with a machine, particularly manually. The stress at an averagein the length and width direction, as a value for practical use, at 100%elongation is 100 to 800 g/cm width, preferably 150 to 600 g/cm width,more preferably 200 to 400 g/cm width. When the film is stretched in thewidth direction for wrapping, the length/width balance is preferably 5/1to 1/1, more preferably 5/1 to 4/3. The former value (5/1) is set due tonecking in wrapping by stretching the film and a failure in cutting.

Second, the stress at 200% elongation, expressed as above, is 200 to1,000 g/cm width, preferably 250 to 900 g/cm width, more preferably 300to 600 g/cm width. When the film is stretched in the width direction forwrapping, the length/width balance is preferably 5/1 to 1/1, morepreferably 5/1 to 4/3. (When a film is broken just before fullystretched due to insufficient elongation in measurement, data is to beobtained by extrapolation.) These values are preferably applied to thecase of using the film for stretch wrapping.

Viewed from orientation properties, the stress per unit area on average(length and width directions), at 100% elongation, is 1 to 6 kg/mm²,preferably 1.5 to 5.0 kg/mm², more preferably 2 to 4.0 kg/mm². Thestress at 200% elongation under the same conditions is 2 to 10 kg/mm²,more preferably 2.5 to 8.0 kg/mm², further preferably 3.0 to 6.0 kg/mm²,and the balance is at the same level as above.

That is, the film of the present invention preferably has a specificlayer structure in which all the layers are at least unidirectionallycold-oriented. Therefore, when the film wrapping an article is firstloosely stretched in the direction in which the film can be elongated toa greater extent, the stress extends in the direction at right angles tothe direction in which a force is applied, and the film orientation alsoshifts to the direction in which a force is applied to improve the filmstrength. That is, it has been found that the film is oriented bycold-stretching. This fact is because a film obtained by acold-stretching method has a high degree of orientation and a greaterresidual elongation than a film obtained by any other method. It hasbeen found that the stress propagates in every directions to work andthe film in the loosened direction shifts to tightly wrap an article.

Having a specific layer structure, the film of the present inventionshows excellent handling properties, excellent heat resistance,particularly excellent resistance to opening caused by melting of asealing portion in sealing and a wide sealing range. In particular, thefilm or the present invention produces a remarkable effect when asealing portion has a portion folded in two or more and an unfoldedportion under a tray (in that the heat resistance and sealability whichare contradictory to each other should be concurrently satisfied.)Further, the present invention has for the first time succeeded inmaking an extremely thin film usable as a result of remarkableimprovement in the film strength properties and the handling propertiesin addition to the sealability. For example, in a test in a commercialmarket, the film of the present invention having a thickness of 10μ canreplace a plasticized PVC stretch film having a thickness of 16μ andenables the fully sufficient wrapping with satisfying variousrequirements, and the film of the present invention makes the wrappingpossible even if it is an extremely thin film having a thickness of 6μ.It has been found that an article which should be packaged with aplasticized PVC film having a thickness of 26μ due to severe wrappingrequirements can be fully packed with a film having a thickness of 10μ,provided by the present invention, without any problem. Further, thefilm of the present invention is optimum for [shrink+stretch] wrapping,and in this case, it is not always necessary to satisfy the abovevarious requirements for elongation and stress in stretch wrapping.

In such a case, that the characteristic of the low-temperature shrinkproperties further becomes a merit by a wrapping system, consists in anexcellent point that a portion near a sealed portion of the film or theentire film shrinks by heat of the sealed portion in sealingconcurrently with sealing and wrapping is completed tight. Further, thefilm of the present invention permits complete wrapping with excellentheat efficiency without altering a wrapped article with heat by a simplemethod in which there is used hot air having a lower temperature thanthat used in a shrink wrapping method, a sealed portion is covered tokeep the heat of the sealed portion or air is additionally stirred. Theabove stretch and shrink wrapping-like wrapping with a film has not yetbeen achieved, and can be one of the fields where the features of thefilm of the present invention can be worked.

The use and fields of the film of the present invention have beendescribed above. However, the present invention shall not be limitedthereto. The film of the present invention is a remarkable film usablefor various uses, and no special limitation is imposed on the use of thefilm of the present invention.

Further, the film of the present invention has a well balance ofcontradictory properties such as a combination of heat resistance,shrinkability and sealability, that of tear strength and a filmthickness, and that of rigidity of a film and easiness in elongation.For example, in the relationship between the heat resistance value[T_(H) ]°C. and the sealing temperature value [T_(s) ]°C. measured bymethods specified in Examples to be described later, the value of [T_(H)-T_(s) ] is at least 15° C., preferably at least 25° C., more preferablyat least 35° C.

Production of multi-layered film

The process for producing the film, provided by the present invention,will be described hereinafter. However, the present invention shall notbe limited thereto.

In a preferred embodiment of the process of the present invention, theraw materials are individually thermoplasticized and melted withseparate extruders so as to form the above polymer compositions and thelayer structures and extruded through a multi-layer die after thesematerials are allowed to converge inside the die or before the die, orseparately extruded resin films are consecutively coated one on another,and the resultant product is solidified by rapidly cooling it to form asufficiently uniform, tubular or sheet-shaped raw film. Alternatively,raw films are separately prepared by extrusion and laminated one on theother. In the present invention, it is preferred to employ a method inwhich the raw materials are co-extruded through an annular, multi-layerdie to form a tubular raw film although the present invention shall notbe limited thereto.

The above-obtained raw film constituting the above layers may bepretreated with high-energy beam as required, for example, with electronbeam, gamma ray or ultraviolet ray at a dose of 1 to 10 megarad,preferably 2 to 7 megarad. For example, a variety of electron beamirradiation apparatus producing an electron beam energy of 100 to 1,000KV are advantageously used, although the apparatus is not speciallylimited. The irradiation may be carried out from one side only or fromboth sides. The depth degree of electron beam penetration may becontrolled by adjusting irradiation energy. The sensitivity of the resinof each layer of the multi-layered film in the film thickness directionmay be changed, for example, on the basis of the molecular weight(relating to melt flow rate) of each resin, the kind of comonomers to becopolymerized, a blend of resins having different crosslinkingcapability or incorporation of an additive to promote or inhibit thecrosslinking. For example, the crosslinking degree (represented by gel%) of one surface or both surfaces of the film or any internal layer maybe increased or decreased, an intended layer alone may be crosslinked, ablend component may be mainly crosslinked, and the sealability (wideningof the upper and lower limits of the temperature for sealing) may begreatly improved by keeping the crosslinked degree of an intended layer(e.g., surface layer) low, or increasing the crosslinked degree of atleast one internal layer. In some cases, crosslinking at so low a levelthat cannot be represented by gel % (e.g., to an extent that MI of anintended layer is decreased), i.e., low-level treatment may be carriedout. Further, the film may be modified by causing gradient crosslinkingamong the layers in the film thickness direction or in one layer. Inthis case, desirably, the heat resistance, sealability, surfacemodification (lubricity, anti-fogging property and optical properties),various strengths and stretchability are sometimes greatly improved.Further, the stretched film may be treated in the same manner as above.

The excessive crosslinking treatment brings an unfavorable result onvarious properties.

Then, the raw film is heated up to no more than 120° C., or as it is(room temperature), and the film is cold-stretched at a stretchtemperature between 110° C. and 30° C. at an area stretch ratio of 4 to30 times. This stretch temperature refers to the temperature at astretch initiation point. When the film is used for stretch-applied userather than shrink-applied use, the lower temperature range ispreferred. In particular, the feature is that the stretchability of thefilm is more improved by allowing the film to shrink at 40 to 100° C. atan arbitrary ratio lengthwise and widthwise but at a total ratio of 5 to80%, preferably 10 to 60% (area) before or after, or before and after anip roll after deflating of a bubble after the film is stretched in theprocess. In this case, the temperature for the treatment is 40° to 90°C., more preferably 45° to 80° C. In this case, the shrink ratio is morepreferably 10 to 50 (area) %. The lower limits of the temperature andthe shrink ratio is determined in view of the imparting ofstretchability. The upper limit of the temperature is determined in viewof the film strength, deterioration of the optical properties and aproblem of film blocking during the process. The upper limit of theshrink ratio is determined in view of a problem that an uneven thicknessin the film width direction occurs.

Preferred embodiments will be described hereinafter. However, thepresent invention shall not be limited thereto.

Heating of the above raw film is carried out generally at 120° C. orlower, preferably at 110° C. or lower, more preferably 100° C. or lower.Further preferably, the raw film is heated to a temperature at which themain crystal component is not melted in any one of the base layer (SBClayer), the surface layer (S layer) and the auxiliary layer (R layer),secondly preferably in the two of these layers and thirdly preferably inthe all layers and at which the properties obtained by the rapid coolingas mentioned above are not damaged, and then inflated in the form ofbubble and sufficiently stretched at a temperature not higher than 110°C., preferably 35°-105° C., more preferably 35°-100° C., furtherpreferably 35°-90° C., and then at a temperature of 40°-80° C. and at atemperature lower than the melting point of the crystal component usedin the composition of the above layers, further preferably at atemperature of not higher than the Vicat softening point of the polymeror the mixture used as a main component under sufficient internalpressures, whereby the intended film can be obtained. The above stretchtemperature conditions are preferably applied to all layers, but in somecase the conditions may not be restricted by the melting point or theVicat softening point depending on the kind of the main componentscontained in the surface layer (S layer), the base layer (SBC layer) orthe auxiliary layer (R layer). This is because the above restriction isnot so significant when the composition is, for example, a softcomposition or a composition containing resin of low crystallinity orfree of crystal. The optimum area stretch ratio in this case variesdepending on composition, construction of layers and temperature at thattime, but is generally 4-30 times, preferably 5-20 times and widthwisestretch ratio conducted in the preferred case of biaxial stretching isgenerally 2-6 times, preferably 2-4 times. In this case, as conditionsin order that cold stretching can be sufficiently attained withinhibiting puncture, important are compositions within theabove-mentioned ranges and the above-mentioned combination of layers,and besides, preparation of sufficiently uniform raw film is important.However, it is the preferred method for carrying out the stretching moststably to stretch the raw film to the extent at which inflation inwidth-wise direction of the bubble stops and to immediately deflate atthe portion of the maximum diameter by driving roll type deflator. Inview of the relation between internal pressure and diameter, the rawbubble has a diameter of about 30 mm or more, preferably 50 mm or moreand conveniently has a large size as far as the apparatus permits. Byadding the above-mentioned auxiliary layer (R layer), stability ofstretching is obtained and especially, there is obtained the effect thatpuncture occurs quite a few even in the case of extremely thin film.Furthermore, it has been found that when the auxiliary layer (R layer),the core layer (H layer) and other layers are dividedly arranged,further conspicuous effect is exhibited and even the surprisinglyextremely thin film of 4 μm with totally 7 layers can be more stablysubjected to continuous stretching at 45° C. This effect has beenconspicuously superior to that of JP,A 60-79932 (corresponding to U.S.Pat. No. 4,619,859).

The whole layer is uniformly, stably and highly stretched by the featureof the present process of less heat transfer and besides, by thesynergistic effect of each layer in the multi-layer being highlystretched and as a result, the film having the above-mentionedcharacteristics can be obtained. Moreover, film thickness of fromextremely-thin level to thick level can be freely obtained. Further,ultra-high speed stretching has become possible for the first time andproduction of low cost films has become possible.

The above effects cannot be obtained by the conventional stretchingmethod of heating the raw film to higher than the melting point.Especially, in such method, the stretching temperature must be furtherraised for improving the optical characteristics and as a result, inmany cases, it becomes further difficult to apply orientation andstrength tends to decrease.

The same thing can be said in the case of the temperature of meltingpoint ±5° to 10° C. and not only the optical characteristics are notfurther improved, but also puncture occurs due to the temperature atwhich brittleness of raw film results or high characteristics cannot beimparted in the case of mixed composition. Especially, when differentresins are combined in multi-layer, the resins differ in theirrespective optimum stretching temperature and stretching of all layersis impossible in many of the combinations and normally in many cases,impartment of orientation by stretching of either layer is sacrificedwhile according to the present method, stretching orientation can beeffectively imparted to all layers or layers of as many as possible.

To effectively apply the stretching of the present invention at very lowtemperatures has never been attained. For example, at 40° C. as inExample 12 given hereinafter, this has been attained for the first timeby the synergistic effects of using a uniformly rapidly cooledmulti-layered tube containing the specific copolymer layer andsatisfying conditions of specific stretching method.

The heating temperature herein used is the maximum temperature of rawfilm before subjected to stretching in the stretching part and thestretching temperature herein used is the temperature of the part atwhich the stretching is started and naturally the temperature furtherlowers by cooling from that part towards the region in which thestretching is terminated. It is desired in the stretching terminationregion (region in which diameter of bubble reaches maximum) tosufficiently cool to 45° C. or lower, preferably 35° C. or lower andmore preferably 30° C. or lower. Therefore, it is desired that thedifference in temperature of the stretching starting part and thestretching terminating part is at least 5° C., preferably at least 10°C. and more preferably at least 15° C. These temperatures are thosewhich are measured at the surface of bubble by a contact thermometer.Furthermore, for example, in the case of Run No. 65 of Example 12,temperature of the stretching starting region was 53° C., andtemperature at 1/3 length from raw film in the region during inflationbetween bubble of maximum diameter and raw film was 50° C., temperatureat 2/3 length was 39° C. and temperature in the stretching terminatingregion was 20° C. From the above, it can be seen that the method of thepresent invention is a novel cold stretching method. Furthermore, whenshrinkability is regarded to be important, it is preferred in some caseto carry out the stretching at higher temperature side in theabove-mentioned range in view of dimensional stability, elastic recoveryafter shrink and high shrink characteristics.

In order to smoothly carry out the cold high stretching, the stretchingin this case is preferably carried out with blowing the air controlledin its temperature by an air ring to the bubble during heating andstretching and with controlling air flow over the surface layer portionas uniformly as possible. The heating temperature of raw film, one whichdoes not exceed by 20° C. over the temperature of the stretchingstarting part is preferable for stability of bubble.

As one method for controlling air flow near the surface layer portion,there is a method according to which fluid (gas) accompanied on thesurface of the film and the boundary film are discontinuously contactremoved in circumferential direction by a rectification contacting guideused for substantial separation of the heating part and the stretchingstarting part, thereby to remove non-uniformity caused by mutual actionof the heating part, the stretching starting part and the cooling part.This controlling method can be similarly used in the stretching startingpart, the stretching part and the stretching terminating region.Internal pressure in the bubble is high and it is preferred tosufficiently highly stretch the bubble under a high pressure,preferably, 100-5000 mmH₂ O (for raw film of 200μ and 100 mmφ) and morepreferably 200-2000 mmH₂ O. Furthermore, the film of the presentinvention may be subjected to the aforementioned crosslinking treatmentafter stretching.

The film of the present invention has the excellent properties asmentioned above and simultaneously has very uniform section afterstretching. It is considered that this is because a high extension poweris applied to the film by the high bubble internal pressure and thermalhistory of heating and cooling is especially small as compared with theconventional production method, resulting in high uniformity andstability. There is the characteristic that even if the opticalcharacteristics (both the haze and the gloss) appear somewhat inferiorin the stage of raw film, they become much superior after coldstretching. Furthermore, by employing the multi-layers as mentionedabove, stability in processing is remarkably improved as compared withemploying a single layer, and uniform and high quality products can beobtained.

For example, in the case of PP single layer, the film can be stretchedat a temperature in a very narrow range of about 140°-160° C. andmoreover the stretching is difficult and continuous stretching can beattained only under severe conditions. When the temperature is lowerthan the above range, puncture occurs and stretching is impossible andwhen it is higher than the range, only whitened and weak film can beobtained. In the case of around 80° C. and besides, for example, 37° C.as in the Example of the present invention, stretching cannot beattained at all and in this respect, too, the effect of the presentinvention is utterly surprising.

The characteristics obtained are also superior to those in the case ofsingle layer, for example, in optical characteristics, low-temperatureshrinkability, sealability, tear strength, and impact strength andnormally, the film of the present invention can be stretched to thelevel higher than conventional film. The film of the present inventionto be finished as a film for stretch wrapping is characterized in thatin addition to selection of the resin compositions of respective layers,it is subjected to heat treatment freely on-line or after winding upafter stretching to partially release degree of orientation to impartelongation and cold stretchability and shift of orientation betweenlength direction and width direction can be freely attained.

Specifically, the present invention provides an at least monoaxiallystretched and oriented high strength multi-layered film which has alayer constitution of at least five layers comprising at least one layercontaining a specific mixed composition which improves mainlystretchability, a layer mainly composed of at least one hard polymerselected from crystalline polypropylene, crystalline polybutene-1 andcrystalline poly-4-methylpentene-1 which improves elastic modulus andheat resistance of the film, an auxiliary layer which mainly furtherimproves strength of the film, and a surface layer which improves mainlyoptical characteristics of the surface, anti-fogging proparty andsealability. This film is excellent in especially tear strength andimpact strength in addition to heat resistance, low-temperatureshrinkability and stretchability and is a packaging film superior inpractical wrapping properties and furthermore, this film has sufficientpracticality even in the form of extremely-thin film which has not beenattained until now and is excellent in cost and performance. Uses ofthis film include shrink wrapping, stretch wrapping, stretch-shrinkwrapping and besides, skin pack wrapping, tight-contact householdwrapping, non-shrink wrapping, and soft deep-drawn wrapping. Thus, thefilm of the present invention is industrially very useful.

EXAMPLES

The present invention will be explained by the following examples andcomparative examples.

EXAMPLE 1

Mixed composition for SBC layer (M₁):

a₁ : Ethylene-vinyl acetate copolymer (EVA) [Content of vinyl acetategroup: 13% by weight; MI: 1.0; mp: 95° C.; VSP: 79° C.]: 35% by weight.

a₃ : Linear low-density polyethylene (LLDPE) [Copolymer of ethylene with10% by weight of octene-1 as the α-olefin, MI: 3.3; VSP: 85° C.; mp:120° C. (main peak in the high temperature side); density: 0.912 g/cm³]: 30% by weight.

b₁ : Ethylene-α-olefin copolymer thermoplastic elastomer [Randomcopolymer with 15 mol % of propylene as the α-olefin and 3% by weight ofethylidene-norbornene, MI: 0.45; VSP: 40° C. or lower; density: 0.880g/cm³ ; noncrystalline]: 15% by weight.

c₁ : Crystalline polypropylene (IPP) [Polypropylene homopolymer, MFI:3.3; mp: 160° C.; VSP: 153° C.; density: 0.90 g/cm³ ]: 15% by weight.

c₂ : Crystalline polybutene-1 (PB-1) [MI: 4.0; density: 0.900 g/cm³ ;VSP: 81° C.; mp: 86° C.]: 5% by weight.

The above resins were mixed (VSP: 78° C.) and 5 parts by weight (basedon 100 parts by weight of the mixed resins) of the following AS agent isadded thereto.

AS₁ : Hydrogenated cyclopentadiene resin [Softening point: 125° C.measured by ring and ball method].

The resulting mixture is kneaded.

Mixed composition for H layer (H₁):

IPP (C₁): 70% by weight and PB-1 (C₂): 30% by weight are mixed.

R layer:

LLDPE (a₃)

S layer:

a₂ : EVA [Content of vinyl acetate group: 14% by weight; MI: 2.0; mp:88° C.; VSP: 74° C.]

The above components are thermoplasticized and melt mixed at a cylindermaximum temperature of 220° C. by the following four extruders,respectively: an extruder having a screw of 50 mm in diameter (L/D=37)and an injection port at the position of L/D=8 from the tip portion, anextruder having a screw of 40 mm in diameter (L/D=29), an extruderhaving a screw of 40 mm in diameter (L/D=37) and an injection port atthe position of L/D=8 from the tip portion, an extruder having a screwof 40 mm in diameter (L/D=37) and an injection port at the position ofL/D=8 from the tip portion. In this case, from the injection port ofextruders for R layer, S layer and SBC layer, two anti-fogging agents ofglycerin monooleate and diglycerin monooleate are injected so that eachof the layers contained the anti-fogging agents in an amount of 1.5% byweight each and totally 3.0% by weight and are kneaded. Respectivekneaded products are extruded from an annular die having 7 layers of 4kinds and rapidly cooled by a water cooling ring provided at theposition of 6 cm from the tip of the die which uniformly dischargeswater to obtain a raw film of 180 mmφ (Run No. 1 in Table 1). Variousraw films were obtained in the same manner as above except thatcompositions of the S layer and the R layer are changed as in Run Nos.2-8.

Unevenness (circumferential direction) in thickness of the resultingfilms was within ±2%. Each of these raw films is passed between twopairs of carrying nip rolls and take-off nip rolls, where the films areheated to 55° C. for Run Nos. 1-5 and to 45° C. for Run Nos. 6-8 andthen air is introduced into the films as they are and the films arecontinuously inflated by the above-mentioned rectification contact guideto stretch them to nearly 3.2-3.6 times in length direction and 3.2-3.7times in width direction. The films of stretching terminated area arecooled by an air ring from which cold air of 18° C. is jetted, folded bya deflator, and taken off by nip rolls and air of 50° C. is blownagainst the films of Run Nos. 1-5. Then, films of Run Nos. 1-5 areshrunk by 10% in length direction and by 30% in width direction in azone between two pairs of inlet nip rolls and outlet nip rolls, speed ofthe 1 latter being slower 10 or 15% than that of the former. For thefilms of Run Nos. 6-8, air of 60° C. is blown against the films andthese are shrunk by 15% in length direction and 40% in width directionin a zone between two pairs of nip rolls, speed of outlet nip rollsbeing slower 15%. Thereafter, these films are simultaneously subjectedto heat setting stabilization treatment and edge portions of each filmare slit to separate into two films, which are respectively wound up tothe predetermined tension to obtain desired films having a giventhickness. Table 2 shows various characteristic values of the resultingfilms and commercially available five films (a), (b), (c), (d), and (e).

It is clear that the films of Run Nos. 1-8 has stable stretchability,has no stain on the surface and are excellent in unti-fogging propertyand thus are superior to the samples of comparative examples.

Furthermore, all of the films of the present invention are superior instretchability to the degree of extremely thin film. For example, whenthe raw film comprising the combination of layers of Run No. 4 isthinned as above and stretched and heat treated in the same manner asabove to obtain finally a film of 4μ thick (OF-1), surprisingly thestretching is very stable with few punctures. For comparison, the sameraw film from which R layer is omitted and the same raw film from whichR layer is similarly omitted and in which H layer is provided at thecenter portion of SBC layer are thinned to the same thickness and arestretched and stretchability is examined to find that these are bothinferior in stretchability (evaluated by the number of punctures). Thenumbers of punctures of these three films in terms of the number per 1hour are 2, 15 and 30, respectively. Tear strength also are decreased inthis order. Other characteristics of the former film are all within thepreferred ranges of the present invention.

Furthermore, the former film of the present invention is obtained in thesame manner and is passed between Teflon-coated heating rolls andinstantaneously pressed to cause blocking of the seventh layers insideof the bubble to obtain a double film (having totally 14 layers andhaving a total thickness of 8 μm). Tear strength of this film ismarkedly improved, namely, 110 g. Other characteristics are similarlywithin the preferred ranges.

As practical packaging test, four cucumbers are wrapped with the film ofRun No. 2 by the commercially available fused sealing L type packagingmachine and passed for 2 seconds through a shrinking tunnel in which ahot air of 90° C. is blown. The resulting package is tight and free fromcreases of the film and the film well fitted to the content and thus thecontent is beautifully shrink wrapped in good state withoutdeterioration in optical characteristics after shrinking. Furthermore,the wrapping could be accomplished in good state in a wide range oftemperature from low temperature side and in a wide range of wrappingspeed.

On the other hand, the commercially available polypropylene shrink film((c) of comparative example) scarcely shrunk even at 90° C. for 10seconds and has creases. It could not be sufficiently shrunk unless thetemperature of the hot air is raised to 170° C. and residence time isincreased to 5 seconds. Even when the temperature of the hot air isfurther raised and the residence time is further increased, the film hasholes and is broken or has lost the clarity. Thus, proper temperaturerange is very narrow. Moreover, the commercially available PVC shrinkfilm is still insufficient in shrink even under the above conditions.The temperature must be 150° C. and the time must be 5 seconds. The filmof the present invention is especially high in shrink respondency(speed) and wrapping could be accomplished in 1 second.

Furthermore, the commercially available crosslinked polyethylene shrinkfilm ((b) of comparative example) also does not shrink well unless thetemperature is high (170° C.). A good wrapping is not obtained. Thisfilm is readily broken in the sealed portion and the film per se alsoreadily broken. Further, wrapping capability range is judged afterwrapping by having creases, banding power, holes in the sealed portion,break of the film which begins from air venting holes and loss ofclarity and besides, the degree of finishing to find that the film ofthe present invention is the most excellent.

Furthermore, wrapping is carried out with the film of Run No. 7 byvarious wrapping machines commercially sold as automatic wrappingmachines for stretch wrapping, namely, one type (called pillow type)according to which the film is stretched in width direction along thedirection of flow, the front and rear portions of the film are cut andthe film edge portions are tucked in the front and rear of tray andanother type (called elevator type) according to which the film is cutto a given size and pulled to the four sides and an article on a tray tobe wrapped is pushed up to the said film from underside of the film andthen, the four sides of the film are tucked in underneath the tray. Thewrapping could be performed by any of these wrapping machines withoutcausing problems in respective steps and with good sealing by a hotplate. Furthermore, good wrapping could be obtained using all of thefilms of Nos. 1-8 even if the content is loosely wrapped when a simpletunnel in which hot air of 80° C. is blown, is placed above the sealingpart of the above wrapping machines.

Especially, when an article having projections is wrapped by the film ofthe present invention, no break occurs or even when a hole is formed,break is not propagated while when such article is wrapped byconventional films, break occurs frequently. Furthermore, even whenwrapping is carried out with the film of the present invention by theabove various wrapping machines at increased wrapping speed, goodwrapping free from creases could be obtained.

As explained above, the film of the present invention has many superiorfeatures over conventional films in the use of shrink film andcompletely satisfies the various conditions necessary for this use andbesides, can also be used for conventional stretch wrapping.

Furthermore, when the above mentioned extremely thin film (OF-1) of 4μis tested by the former wrapping machine mentioned above, wrapping couldbe accomplished without causing creases without using a simple shrinktunnel. Moreover, hand stretch wrapping could also be easily performedwithout occurrence of break.

Besides, films of Run Nos. 1-8 and OF-1 (especially, films of Run Nos.6-8 and OF-1) are superior in recovery properties against externaldeformation caused by the projections after stretch (and shrink)wrapping. The film of comparative example (d) does not recover at all,resulting in looseness and permanent deformation.

                  TABLE 1                                                         ______________________________________                                        Layer                                                                         construction of                                                               raw film   1     2      3    4    5    6    7    8                            ______________________________________                                        The first layer                                                                          a.sub.2                                                                             a.sub.1-19                                                                           b.sub.2                                                                            a.sub.8                                                                            a.sub.2                                                                            a.sub.2                                                                            a.sub.2                                                                            a.sub.2                      (S layer) μ                                                                            9     9      9    9    9   6    6    7                            The second layer                                                                         a.sub.3                                                                             a.sub.4                                                                              a.sub.5                                                                            a.sub.6                                                                            a.sub.1                                                                            a.sub.7                                                                            a.sub.1-3                                                                          a.sub.8                      (R layer) μ                                                                            9     9      9    9    9   6    6    7                            The third layer                                                                          H.sub.1                                                                             H.sub.1                                                                              H.sub.1                                                                            H.sub.1                                                                            H.sub.1                                                                            H.sub.1                                                                            H.sub.1                                                                            H.sub.1                      (H layer) μ                                                                           18    18     18   20   18   3    3    4                            The fourth layer                                                                         M.sub.1                                                                             M.sub.2                                                                              M.sub.3                                                                            M.sub.4                                                                            M.sub.5                                                                            M.sub.6                                                                            M.sub.7                                                                            M.sub.8                      (SBC layer) μ                                                                         18    18     18   20   18   36   36   35                           The fifth layer                                                                          H.sub.1                                                                             H.sub. 1                                                                             H.sub.1                                                                            H.sub.1                                                                            H.sub.1                                                                            H.sub.1                                                                            H.sub.1                                                                            H.sub.1                      (H layer) μ                                                                           18    18     18   20   18   3    3    3                            The sixth layer                                                                          a.sub.3                                                                             a.sub.4                                                                              a.sub.5                                                                            a.sub.6                                                                            a.sub.1                                                                            a.sub.7                                                                            a.sub.1-3                                                                          a.sub.8                      (R layer) μ                                                                            9     9      9    8    9   3    3    7                            The seventh layer                                                                        a.sub.2                                                                             a.sub.1-19                                                                           b.sub.2                                                                            a.sub.8                                                                            a.sub.2                                                                            a.sub.2                                                                            a.sub.2                                                                            a.sub.2                      (S layer) μ                                                                            9     9      9    9    9   6    6    7                            Total thickness                                                                          90    90     90   95   90   60   60   70                           (μ)                                                                        ______________________________________                                    

The marks in Table 1 indicate the following resins or resincompositions.

a₄ : Linear low-density polyethylene [Copolymer of ethylene with 9% byweight of 4-methylpenten-1 as α-olefin, MI: 3.6; VSP: 92° C.; density:0.910 g/cm³ ]

a₅ : Linear low-density polyethylene [Copolymer of ethylene with 9% byweight of hexene-1 as α-olefin, MI: 3.2; VSP: 92° C.; density: 0.912g/cm³ ]

a₆ : Linear low-density polyethylene [Copolymer of ethylene with 7% byweight of 4-methylpentene-1 as α-olefin, MI: 2.0; VSP: 109° C.; density:0.930 g/cm³ ]

a₇ : EAA [Content of acrylic acid group: 15% by weight; MI: 5; mp: 95°C.; VSP: 65° C.]

a₈ : EVA-AA [Content of vinyl acetate group: 4.0% by weight and contentof acrylic acid group: 8% by weight; MI: 6; mp: 102° C.; VSP: 70° C.]

M₂ -EVA (a₁): 35% by weight; linear low-density polyethylene (a₄): 30%by weight; elastomer (b₁): 15% by weight; IPP (c₁): 15% by weight; PB-1(c₂): 5% by weight.

M₃ -EVA (a₁): 35% by weight; linear low-density polyethylene (a₅): 30%by weight; elastomer (b₁): 15% by weight; IPP (c₁): 15% by weight; PB-1(c₂): 5% by weight.

M₄ -EVA (a₁): 35% by weight; linear low-density polyethylene (a₆): 30%by weight; elastomer (b₁): 15% by weight; IPP (c₁): 15% by weight; PB-1(c₂): 5% by weight.

M₅ -EVA (a₁): 65% by weight; elastomer (b₃): 15% by weight; IPP (c₁):15% by weight; PB-1 (c₂): 5% by weight.

M₆ -EVA (a₁): 35% by weight; EAA (a₇): 30% by weight; elastomer (b₁):20% by weight; IPP (c₁): 10% by weight; PB-1 (c₂): 5% by weight.

M₇ -EVA (a₁): 35% by weight; linear low-density polyethylene (a₃): 30%by weight; elastomer (b₁): 20% by weight; IPP (c₁): 10% by weight; PB-1(c₂): 5% by weight.

M₈ -EVA (a₁): 35% by weight; EVA-AA (a₈): 30% by weight; elastomer (b₁):20% by weight; IPP (c₁): 10% by weight; PB-1 (c₂): 5% by weight.

a₁₋₃ -EVA (a₁): 30% by weight; linear low-density polyethylene (a₃): 70%by weight.

a₁₋₁₉ -EVA (a₁): 30% by weight; linear low-density polyethylene (a₁₉ :mentioned hereinafter): 70% by weight; VSP of the composition: 81° C.

b₂ -Ethylene-α-olefin copolymer elastomer (copolymerized with 10 mol %of butene-1 as α-olefin); density: 0.895 g/cm³ ; VSP: 60° C.; mp: 116°C.; crystallinity: 15%.

b₃ -Propylene-butene-1 copolymer elastomer (butene-1: 30 mol %);density: 0.880 g/cm³ ; VSP: 45° C.; mp: 78° C.; crystallinity: 9.0%.

                                      TABLE 2                                     __________________________________________________________________________                         Run No.                                                  Characteristics                                                                             unit   1     2     3     4     5     6                          __________________________________________________________________________    Haze          %        0.6   0.7   0.7   1.0   0.5   0.5                      80° C. shrinkage                                                                     %      37    38    38    35    35    35                         Tensile break strength                                                                      Kg/mm.sup.2                                                                            16.2                                                                                15.9                                                                                16.5                                                                                16.9                                                                                15.1                                                                                9.6                      Tensile break elongation                                                                    %      220   240   230   250   280   330                        Stress at 100% elongation                                                                   g/cm   860/  830/  820/  850/  850/  300/                       (length direction/                                                                          width  220   230   270   300   250   150                        width direction)                                                              Stress at 200% elongation                                                                   g/cm    --/   --/   --/  1650/ 1150/ 580/                       (length direction/                                                                          width  550   560   520   530   470   320                        width direction)                                                              Sealing temperature (Ts).sup.×1                                                       °C.                                                                           87    85    86    87    85    85                         Heat resisting temperature                                                                  °C.                                                                           155   158   156   159   155   150                        (Ts).sup.×2                                                             Anti-fogging property.sup.×3                                                          --     ⊚                                                                    ⊚                                                                    ⊚                                                                    ⊚                                                                    ⊚                                                                    ⊚           Sealability.sup.×4                                                                    --     ⊚                                                                    ⊚                                                                    ⊚                                                                    ∘                                                                       ⊚                                                                    ⊚           Tear strength g      26    25    27    39    17    43                         Stiffness.sup.×5                                                                      mg     45    42    49    49    41    29                         Thickness of film                                                                           μ   10    10    10    10    11    10                         __________________________________________________________________________                       Run No.                                                                               Compara-                                                                            Compara-                                                                            Compara-                                                                            Compara-                                                                            Compara-                   Characteristics                                                                             unit 7   8   tive (a)                                                                            tive (b)                                                                            tive (c)                                                                            tive (d)                                                                            tive                       __________________________________________________________________________                                                       (e)                        Haze          %      0.8                                                                               0.7                                                                                1.7                                                                                 2.5                                                                                 2.8                                                                                 2.0                                                                                 2.0                     80° C. shrinkage                                                                     %    32  37   33    5     3     0     0                         Tensile break strength                                                                      Kg/mm.sup.2                                                                          10.8                                                                              9.5                                                                                8.0                                                                                 6.9                                                                                12.0                                                                                 2.2                                                                                 3.1                     Tensile break elongation                                                                    %    380 370 150   110   110   300   280                        Stress at 100% elongation                                                                   g/cm 280/                                                                              280/                                                                               500/ 1100/ 1500/  200/  350/                      (length direction/                                                                          width                                                                              150 160 140   1200  1600  120   150                        width direction)                                                              Stress at 200% elongation                                                                   g/cm 570/                                                                              540/                                                                              --/-- --/-- --/--  250/  500/                      (length direction/                                                                          width                                                                              320 330                   140   250                        width direction)                                                              Sealing temperature (Ts).sup.×1                                                       °C.                                                                         85  83  160   170   175   100   180                        Heat resisting temperature                                                                  °C.                                                                         150 150 150   165   170    95   165                        (Ts).sup.×2                                                             Anti-fogging property.sup.×3                                                          --   ⊚                                                                  ⊚                                                                  Δ                                                                             Δ                                                                             X     ∘                                                                       ∘              Sealability.sup.×4                                                                    --   ⊚                                                                  ⊚                                                                  Δ                                                                             Δ                                                                             X     X     X                          Tear strength g    46  40   2     4     4    100   100                        Stiffness.sup.×5                                                                      mg   25  22   50    12    60    7     6                         Thickness of film                                                                           μ 11  10    13.5                                                                               15    15    21    16                        __________________________________________________________________________      1 [Sealing temperature]

A commercially available tray (10 cm×20 cm) made of high-impact styrolis wrapped with the film and two-fold and four-fold portions of the filmare formed under the bottom of the tray and these portions are pressedunder a force of 2 g/cm² for 3 seconds to seal the film. The sealingtemperature is the lower limit of temperature at which the portions canbe sealed without causing peeling of the film when the edge portion ofthe film is lightly pulled.

2 [Heat sealing resisting temperature]

This is the temperature at which hole is formed in some place of thefilm when the folded portion of the film in the above 1 is pressed under4 g/cm² for 3 seconds. In the case of the thickness of the film being20μ or more, the two-ply portion of the film is evaluated.

3 [Anti-fogging property]

The film is spread over a container containing water of about 15° C. andthis is left in a refrigerator at 5° C. for 10 minutes and thereafter,state of waterdrops formed and sticking to the film is observed.

⊚: A uniform water film is formed and the inside can be completely seenthrough the film.

◯: A water film is formed, but has irregularity and the inside isdistortedly seen.

Δ: Large waterdrops stick to the film and the inside can be merelypartially seen.

x: Waterdrops stick to the film and the inside cannot be seen at all.

4 [Practical sealability]

Two oranges are put on a tray made of expanded polyethylene and theseare hand wrapped by a commercially available hand wrapper for stretchpackaging and sealability at the bottom portion by a hot plate isexamined by selecting optimum temperature.

⊚: The whole area of the bottom portion is nearly completely sealedunder the condition of wide temperature range.

◯: 60-80% of the whole area is sealed.

Δ: The bottom portion is spottedly sealed, but holes are formed when itis attempted to seal the whole area.

x: A part is sealed and other part is molten to form holes.

5 [Loop stiffness strength]

A sample of 25 mm in width and 250 mm in length is curved in the form ofloop (length of loop: 60 mm) and the load (mg) when the loop is squashedin the direction of diameter is measured by loop stiffness tester D-Rmanufactured by Toyo Seiki Seisakusho Co. and this is taken as stiffness(average value of length and width directions).

6 Gloss is measured in accordance with ASTM-D523-67 at an angle of 45°(Table 10 given hereinafter).

Comparative sample (a) is a commercially available PVC shrink filmplasticized to a middle degree (20% by weight).

Comparative sample (b) is a commercially available crosslinkedpolyethylene shrink film.

Comparative sample (c) is a commercially available PP shrink film.

Comparative sample (d) is a commercially available non-stretched typestretch film (EVA containing 20% by weight of VAc group).

Comparative sample (e) is a commercially available highly plasticizedPVC stretch film (containing 31% by weight of plasticizer).

The tensile characteristic in Table 2 is expressed by average value inlength and width directions (same in all other Examples).

EXAMPLE 2

Films of Run Nos. 9-10 are obtained in the same manner as in preparationof the film of Run No. 1 in Example 1 except that arrangement of thelayers and thickness of each layer are changed as shown in Table 3.However, heat setting stabilization treatment after stretching iscarried out by blowing air of 50° C. to the films to shrink by 10% inlength direction and by 30% in width direction. Characteristics of theresulting films are shown in Table 4.

Four cucumbers are wrapped with the resulting film in the same manner asin Example 1 by the commercially available L type wrapping machine usinga shrinking tunnel. The film tightly fitted to the content withoutoccurrence of creases to obtain good wrapping. Optical characteristicsafter shrinking does not deteriorate to obtain a beautiful shrinkwrapping.

Furthermore, a crab with arms or a frozen fish as articles havingprojections to be wrapped is wrapped with the film in the same manner asabove to find no break which might be caused by the projections andshrink wrapping with good finishing could be performed.

Furthermore, when wrapping is carried out by various stretch wrappingmachines with a simple tunnel as used in Example 1, there occurs noproblems.

                  TABLE 3                                                         ______________________________________                                        Layer construction of                                                         raw film             9     10                                                 ______________________________________                                        The first layer      a.sub.2                                                                             a.sub.2                                            (S layer) μ        9     9                                                 The second layer     M.sub.1                                                                             M.sub.1                                            (SBC layer) μ      9     9                                                 The third layer      H.sub.1                                                                             H.sub.1                                            (H layer) μ       18    14                                                 The forth layer      a.sub.3                                                                             a.sub.3                                            (R layer) μ       18    27                                                 The fifth layer      H.sub.1                                                                             H.sub.1                                            (H layer) μ       18    13                                                 The sixth layer      M.sub.1                                                                             M.sub.1                                            (SBC layer) μ      9     9                                                 The seventh layer    a.sub.2                                                                             a.sub.2                                            (S layer) μ        9     9                                                 Total thickness      90    90                                                 (μ)                                                                        ______________________________________                                    

                  TABLE 4                                                         ______________________________________                                                             Run No.                                                  Characteristics  unit      9       10                                         ______________________________________                                        Haze             %           0.7     0.9                                      80° C. shrinkage                                                                        %         35      33                                         Tensile break strength                                                                         Kg/mm.sup.2                                                                               16.2    16.8                                     Tensile break elongation                                                                       %         230     230                                        Stress at 100% elongation                                                                      g/cm      830/260 800/220                                    (length direction/                                                                             width                                                        width direction)                                                              Stress at 200% elongation                                                                      g/cm       --/540  --/500                                    (length direction/                                                                             width                                                        width direction)                                                              Sealing temperature                                                                            °C.                                                                              86      85                                         Heat resisting temperature                                                                     °C.                                                                              158     155                                        Anti-fogging property                                                                          --        ⊚                                                                      ⊚                           Sealability      --        ⊚                                                                      ⊚                           Tear strength    g         36      47                                         Stiffness        mg        44      40                                         Thickness of film                                                                              μ      10      10                                         ______________________________________                                    

EXAMPLE 3

Films of Run Nos. 11-14 and Comparative Run Nos. 1-3 are obtained in thesame manner as in preparation of the film of Run No. 6 in Example 1using raw films having compositions of the respective layers and thearrangement of the layers as shown in Table 5. However, for Run. Nos.11-13 and Comparative Run No. 1, the heat setting stabilizationtreatment after stretching is carried out by blowing air of 50° C. tothe film to shrink by 10% in length direction and by 30% in widthdirection and for Run No. 14 and Comparative Run Nos. 2-3, the heatsetting stabilization treatment after stretching is carried out byblowing air of 60° C. to the film to shrink by 15% in length directionand by 40% in width direction. Characteristics of the resulting filmsare shown in Table 6.

The resulting films of the present invention are excellent in variouscharacteristics and are superior to the samples of the comparativeexamples.

When wrapping is carried out with the films of Run Nos. 11-13 forpractical wrapping test using the above-mentioned L type wrappingmachine, the films tightly fitted to the content with no creases toobtain good wrap and thus beautiful shrink wrapping could be attainedwithout deterioration of optical characteristics after shrinking.Further results are obtained that the content could be wrapped well in awide temperature range from lower temperature side and a wide speedrange. Moreover, when an article having projections is wrapped as inExample 2, good shrink wrapping could be attained with no breaks.

On the other hand, when the same wrapping is carried out with the filmof Comparative Run No. 1, stiffness of the film is insufficient andhandling is somewhat difficult when the film is used in the form of athin film. Furthermore, break occurred frequently when an article havingprojections is wrapped therewith. Moreover, in the case of the film ofthe present invention, wrapping could also be performed with no problemsusing various stretch wrapping machine with a simple tunnel. When thefilm of Run No. 14 is subjected to wrapping tests by various stretchwrapping machine mentioned above, problems in wrapping step are clearedin all of the wrapping machines and sealing by hot plate issatisfactory. When an article having projections is wrapped by variouswrapping machines mentioned above, substantially no break occurs or evenif a break occurs, it does not propagate in the case of the film of RunNo. 14. That is, when the film of the present invention is used, stretchwrapping superior in finish with neither a break nor a crease can beattained even when wrapping speed is increased. Moreover, the wrappingis superior in recovery from deformation caused by the projections underexternal force.

On the other hand, when the above stretch wrapping is carried out withthe films of Comparative Run Nos. 2-3, stiffness of the films isinsufficient and running properties in various portions of the wrappingmachine are inferior. Therefore, wrapping finish is somewhat inferiorand loose wraps are recognized.

Furthermore, when an article having projections is wrapped, break occursfrequently and only the wrapping low in stretching with creases could beobtained. In addition to such tendencies, the film of Comparative RunNo. 3 is inferior also in heat resistance and is narrow in temperaturerange in which sealing is possible and formed holes in sealed portiondue to variation in temperature of the hot plate.

                                      TABLE 5                                     __________________________________________________________________________    Layer                                                                         construction                           Compara-                                                                              Compara-                                                                              Compara-               of raw film                                                                          11      12      13      14      tive 1  tive 2  tive                   __________________________________________________________________________                                                           3                      The first                                                                            (S layer) a.sub.2                                                                     (S layer) a.sub.2                                                                     (S layer) a.sub.2                                                                     (S layer) a.sub.2                                                                     (S layer) a.sub.2                                                                     (S layer)                                                                             (S layer) a.sub.2      layer   9       9       9      6        9       6       6                     μ                                                                          The second                                                                           (R layer) a.sub.3                                                                     (R layer) a.sub.4                                                                     (H layer) H.sub.3                                                                     (SBC layer) M.sub.1                                                                   (SBC layer) M.sub.9                                                                   (SBC layer)                                                                           (SBC layer)                                                                   M.sub.9                layer   9       9      18      15      18      21      21                     μ                                                                          The third                                                                            (H layer) H.sub.2                                                                     (H layer) H.sub.3                                                                     (SBC layer) M.sub.3                                                                   (R layer) a.sub.3                                                                     (H layer) H.sub.1                                                                     (H layer)                                                                             (R layer) a.sub.3      layer  18      18       9      6       36       6       6                     μ                                                                          The forth                                                                            (SBC layer) M.sub.1                                                                   (SBC layer) M.sub.2                                                                   (R layer) a.sub.5                                                                     (H layer) H.sub.2                                                                     (SBC layer) M.sub.9                                                                   (SBC layer)                                                                           (SBC layer)                                                                   M.sub.9                layer  18      18      18      6       18      21      21                     μ                                                                          The fifth                                                                            (H layer) H.sub.2                                                                     (H layer) H.sub.3                                                                     (SBC layer) M.sub.3                                                                   (R layer) a.sub.3                                                                     (S layer) a.sub.2                                                                     (S layer)                                                                             (S layer) a.sub.2      layer  18      18       9      6        9       6       6                     μ                                                                          The sixth                                                                            (R layer) a.sub.3                                                                     (R layer) a.sub.4                                                                     (H layer) H.sub.3                                                                     (SBC layer) M.sub.1                                                                   --      --      --                     layer   9       9      18      15                                             μ                                                                          The seventh                                                                          (S layer) a.sub.2                                                                     (S layer) a.sub.2                                                                     (S layer) a.sub.2                                                                     (S layer) a.sub.2                                                                     --      --      --                     layer   9       9       9      6                                              μ                                                                          Total  90      90      90      60      90      90      60                     thickness                                                                     (μ)                                                                        __________________________________________________________________________

The marks in Table 5 indicate the following composition of resinmixture.

H₂ -IPP (c₁): 80% by weight; hydrogenated cyclopentadiene resin (As₁):20% by weight.

H₃ -IPP (c₁): 70% by weight; PB-1 (c₂): 15% by weight; hydrogenatedresin of petroleum resin containing C₉ fraction (AS₂): 15% by weight.

M₉ -EVA (a₁): 65% by weight; elastomer (b₁): 15% by weight; IPP (c₁):15% by weight; PB-1 (c₂): 5% by weight.

                                      TABLE 6                                     __________________________________________________________________________                      Run No.                                                                                       Compara-                                                                            Compara-                                                                            Compara-                        Characteristics                                                                            unit 11  12  13  14  tive 1                                                                              tive 2                                                                              tive 3                          __________________________________________________________________________    Haze         %      0.5                                                                               0.6                                                                               0.8                                                                               0.9                                                                               0.6   0.9   0.7                           80° C. shrinkage                                                                    %    38  36  37  32  35    30    32                              Tensile break strength                                                                     Kg/mm.sup.2                                                                          16.2                                                                              16.3                                                                              16.1                                                                              9.1                                                                               12.1                                                                                8.3   8.0                           Tensile break elongation                                                                   %    230 240 240 350 210   260   270                             Stress at 100% elongation                                                                  g/cm 890/                                                                              870/                                                                              890/                                                                              290/                                                                              750/  520/  420/                            (length direction/                                                                         width                                                                              240 250 250 160 330   130   150                             width direction)                                                              Stress at 200% elongation                                                                  g/cm  --/                                                                               --/                                                                               --/                                                                              530/                                                                               --/  900/  680/                            (length direction/                                                                         width                                                                              550 540 520 320 720   350   280                             width direction)                                                              Sealing temperature                                                                        °C.                                                                         86  86  89  85  86    87    85                              Heat resisting temperature                                                                 °C.                                                                         158 153 159 156 157   155   98                              Anti-fogging property                                                                      --   ⊚                                                                  ⊚                                                                  ∘                                                                     ⊚                                                                  ⊚                                                                    ⊚                                                                    ⊚                Sealability  --   ⊚                                                                  ⊚                                                                  ⊚                                                                  ⊚                                                                  ⊚                                                                    ⊚                                                                    Δ                         Tear strength                                                                              g    62  57  63  43   3    15    18                              Stiffness    mg   68  60  86  21  12     8     5                              Thickness of film                                                                          μ 10  10  10  10  10    10    10                              __________________________________________________________________________

EXAMPLE 4

Films of Run Nos. 15-23 are obtained in the same manner as in Example 1using raw films having the compositions of the respective layers andarrangement of the layers as shown in Table 7. However, heat settingstabilization treatment after stretching is carried out by blowing airof 50° C. to the films to shrink by 10% in length direction and by 30%in width direction. Characteristics of the resulting films are shown inTable 8.

The resulting films are superior in all of the characteristics and areespecially high in tear strength. Further, although the films of RunNos. 17 and 18 are extremely thin films of 8μ thick which has never beenseen, they are high in heat resisting temperature in sealing, namely,154° C. and 153° C.

As practical wrapping test, when an article having projections iswrapped with films of Run Nos. 15-18 in the same manner as in Example 2,shrink wrapping of good finish with no break could be obtained.

Furthermore, when a tray pack of an allowance of 20% is wrapped with thefilm of Run No. 19 by L type shrink wrapping machine, the content couldbe tightly wrapped even at a low temperature of 80° C. and besides, thefilm is especially excellent in fused sealing strength at the time ofsealing and cutting operation which comprises sealing simultaneouslywith fusing by hot wire, namely, it is 1.8 kg/cm width. On the otherhand, in the case of Comparative Example (a) shown in Table 2 of Example1, some creases remaines when wrapping is carried out at 100° C. andtight wrapping could be barely performed at 120° C. Fused sealingstrength is 0.3 kg/cm width. When the film of Comparative Example (b) isused, wrapping with no crease is obtained only at 160° C. but cutting isimpossible in sealing and cutting operation and the wrap abnormallydistorted with shrink.

                                      TABLE 7                                     __________________________________________________________________________    Layer construction                                                            of raw film                                                                             15 16 17 18 19 20 21 22 23                                          __________________________________________________________________________    The first layer                                                                         a.sub.4                                                                          a.sub.5                                                                          a.sub.5                                                                          a.sub.4                                                                          a.sub.4                                                                          a.sub.1-4                                                                        a.sub.4-1                                                                        a.sub.4-9                                                                        a.sub.4-10                                  (S layer) μ                                                                           9  9  7  7  9  9  9  9  9                                          The second layer                                                                        M.sub.10                                                                         M.sub.11                                                                         M.sub.12                                                                         M.sub.12                                                                         M.sub.10                                                                         M.sub.1                                                                          M.sub.1                                                                          M.sub.1                                                                          M.sub.1                                     (SBC layer) μ                                                                         9  9  7  7  9  9  9  9  9                                          The third layer                                                                         H.sub.1                                                                          H.sub.1                                                                          H.sub.1                                                                          H.sub.1                                                                          H.sub.2                                                                          H.sub.1                                                                          H.sub.2                                                                          H.sub.1                                                                          H.sub.2                                     (H layer) μ                                                                          18 18 14 14 18 18 18 18 18                                          The fourth layer                                                                        a.sub.3                                                                          a.sub.3                                                                          a.sub.4                                                                          a.sub.5                                                                          a.sub.3                                                                          a.sub.4                                                                          a.sub.4                                                                          a.sub.1-4                                                                        a.sub.1-4                                   (R layer) μ                                                                          18 18 14 14 18 18 18 18 18                                          The fifth layer                                                                         H.sub.1                                                                          H.sub.1                                                                          H.sub.1                                                                          H.sub.1                                                                          H.sub.2                                                                          H.sub.1                                                                          H.sub.2                                                                          H.sub.1                                                                          H.sub.2                                     (H layer) μ                                                                          18 18 14 14 18 18 18 18 18                                          The sixth layer                                                                         M.sub.10                                                                         M.sub.11                                                                         M.sub.12                                                                         M.sub.12                                                                         M.sub.10                                                                         M.sub.1                                                                          M.sub.1                                                                          M.sub.1                                                                          M.sub.1                                     (SBC layer) μ                                                                         9  9  7  7  9  9  9  9  9                                          The seventh layer                                                                       a.sub.4                                                                          a.sub.5                                                                          a.sub.5                                                                          a.sub.4                                                                          a.sub.4                                                                          a.sub.1-4                                                                        a.sub.4-1                                                                        a.sub.4-9                                                                        a.sub.4-10                                  (S layer) μ                                                                           9  9  7  7  9  9  9  9  9                                          Total thickness (μ)                                                                  90 90 70 70 90 90 90 90 90                                          __________________________________________________________________________

The marks in Table 7 indicate the following compositions of mixedresins.

M₁₀ -EVA (a₁): 35% by weight; linear low-density polyethylene (a₃): 20%by weight; linear low-density polyethylene (a₄): 10% by weight;elastomer (b₁): 20% by weight; IPP (c₁): 10% by weight; PB-1 (c₂): 5% byweight.

M₁₁ -EVA (a₁): 35% by weight; linear low-density polyethylene (a₃): 20%by weight; linear low-density polyethylene (a₅): 10% by weight;elastomer (b₁): 20% by weight; IPP (c₁): 10% by weight; PB-1 (c₂): 5% byweight.

M₁₂ -EVA (a₁): 35% by weight; linear low-density polyethylene (a₄): 20%by weight; linear low-density polyethylene (a₅): 10% by weight;elastomer (b₁): 20% by weight; IPP (c₁): 10% by weight; PB-1 (c₂): 5% byweight.

a₁₋₄ -EVA (a₁): 30% by weight; linear low-density polyethylene (a₄): 70%by weight.

a₄₋₁ -EVA (a₁): 70% by weight; linear low-density polyethylene (a₄): 30%by weight.

a₄₋₉ -EEA (a₉): [ethylene-ethyl acrylate copolymer: content of ethylacrylate group: 15% by weight, MI: 1.5, mp: 85° C., VSP: 61° C.]: 30% byweight; linear low-density polyethylene (a₄): 70% by weight.

a₄₋₁₀ -E-AA-BA (a₁₀): [ethylene-acrylic acidbutyl acrylate terpolymer:content of acrylic acid group: 4% by weight and content of butylacrylate group: 8% by weight, MI: 5, mp: 95° C.]: 30% by weight; linearlow-density polyethylene (a₄): 70% by weight.

                                      TABLE 8                                     __________________________________________________________________________                  Run No.                                                         Characteristics                                                                        unit 15  16  17  18  19  20  21  22  23                              __________________________________________________________________________    Haze     %      0.6                                                                               0.6                                                                               0.5                                                                               0.5                                                                               0.7                                                                               0.7                                                                               0.6                                                                               0.7                                                                               0.7                           80° C. shrinkage                                                                %    35  37  33  36  37  35  36  39  34                              Tensile break                                                                          Kg/mm.sup.2                                                                          16.5                                                                              16.3                                                                              17.3                                                                              17.4                                                                              16.9                                                                              15.8                                                                              16.0                                                                              15.7                                                                              15.1                          strength                                                                      Tensile break                                                                          %    220 220 230 220 240 230 230 260 240                             elongation                                                                    Stress at 100%                                                                         g/cm 850/                                                                              870/                                                                              680/                                                                              670/                                                                              850/                                                                              830/                                                                              820/                                                                              860/                                                                              830/                            elongation                                                                             width                                                                              240 250 200 200 260 230 210 240 220                             (length direction/                                                            width direction)                                                              Stress at 200%                                                                         g/cm  --/580                                                                            --/480                                                                            -- /380                                                                           --/460                                                                            --/                                                                               --/                                                                               --/                                                                               --/                                                                               --/                            elongation                                                                             width                590 550 480 500 420                             (length direction/                                                            width direction)                                                              Sealing  °C.                                                                         91  93  93  91  90  89  88  89  88                              temperature                                                                   Heat resisting                                                                         °C.                                                                         157 156 154 153 157 158 156 153 156                             temperature                                                                   Anti-fogging                                                                           --   ⊚                                                                  ∘                                                                     ∘                                                                     ⊚                                                                  ⊚                                                                  ⊚                                                                  ⊚                                                                  ⊚                    property                                                                      Sealability                                                                            --   ⊚                                                                  ⊚                                                                  ⊚                                                                  ⊚                                                                  ⊚                                                                  ⊚                                                                  ⊚                                                                  ⊚                                                                  ⊚                Tear strength                                                                          g    76  73  65  63  74  74  75  74  76                              Stiffness                                                                              mg   57  54  31  36  51  55  50  54  51                              Thickness of film                                                                      μ 10  10   8   8  10  10  10  10  10                              __________________________________________________________________________

EXAMPLE 5

Films of Run Nos. 24-30 and Comparative Run Nos. (4)-(5) are obtained inthe same manner as in preparation of Run No. 1 of Example 1 using rawfilms having the compositions of the respective layers and arrangementof the layers as shown in Table 9. However, heat setting stabilizationtreatment after stretching is carried out by blowing air of 50° C. tothe films to shrink by 10% in length direction and by 30% in widthdirection. The films of Run Nos. 24-30 are all excellent in stretchingprocessability, but many punctures occurs during stretching withespecially the films of Comparative Run Nos. 4 and 5 and stretching isunstable. Characteristics of the resulting films are shown in Table 10.

The resulting films of the present invention are superior in all thecharacteristics, especially low in heat sealing initiation temperatureand high in heat resisting temperature and thus has a wide range ofsealing temperature. For example, the film of Run No. 24 has a sealinginitiation temperature of 78° C. and a heat resisting temperature insealing of 157° C. and thus a sealing temperature range of 79° C. whilethe films of Comparative Run Nos. 4, 5 and 6 has only narrow sealingtemperature ranges of 25° C., 12° C. and -3° C., respectively. Stretchwrapping with the films of Run Nos. 24-30 in the same manner as inExample 1 could be performed without any problems.

The films of Comparative Run Nos. 4 and 5 has the tendency to bewhitened in their surfaces in shrink to deteriorate the transparency.Furthermore, sealed portion on the bottom of the tray is holed to resultin unaccepted articles. Especially, the films of Comparative Run Nos. 5and 6 are entirely unacceptable.

With lapse of time (30° C. for 1 month), the additives over-bled in thefilms of Comparative Run Nos. 4-5 to cause surface tackiness andcontamination of the surface and these films could not be used. On theother hand, the films of Run Nos. 24-30 has no problems.

Moreover, the films of Run Nos. 24-30 are low in lower limit of sealingtemperature and excellent in low-temperature sealability and hence,fresh vegetables (such as cucumbers and egg apples) could be wrappedwithout using trays (burning of the surface of the contents does notoccur).

                                      TABLE 9                                     __________________________________________________________________________    Layer                                                                         construction                                                                  of raw film                                                                          24     25     26     27     28                                         __________________________________________________________________________    The first                                                                            (S layer)                                                                            (S layer)                                                                            (S layer)                                                                            (S layer)                                                                            (S layer)                                  layer μ                                                                           a.sub.7                                                                              a.sub.9                                                                              a.sub.11                                                                             a.sub.12                                                                             a.sub.13                                           9      8      9      9      7                                         The second                                                                           (R layer)                                                                            (R layer)                                                                            (R layer)                                                                            (R layer)                                                                            (R layer)                                  layer μ                                                                           a.sub.4                                                                              a.sub.4                                                                              a.sub.4                                                                              a.sub.4                                                                              a.sub.4                                            9      8      9      9      7                                         The third                                                                            (H layer)                                                                            (H layer)                                                                            (H layer)                                                                            (H layer)                                                                            (H layer)                                  layer μ                                                                           H.sub.1                                                                              H.sub.1                                                                              H.sub.1                                                                              H.sub.1                                                                              H.sub.1                                           18     16     18     18     14                                         The fourth                                                                           (SBC layer)                                                                          (SBC layer)                                                                          (SBC layer)                                                                          (SBC layer)                                                                          (SBC layer)                                layer μ                                                                           M.sub.6                                                                              M.sub.13                                                                             M.sub.14                                                                             M.sub.15                                                                             M.sub.16                                          18     16     18     18     14                                         The fifth                                                                            (H layer)                                                                            (H layer)                                                                            (H layer)                                                                            (H layer)                                                                            (H layer)                                  layer μ                                                                           H.sub.1                                                                              H.sub.1                                                                              H.sub.1                                                                              H.sub.1                                                                              H.sub. 1                                          18     16     18     18     14                                         The sixth                                                                            (R layer)                                                                            (R layer)                                                                            (R layer)                                                                            (R layer)                                                                            (R layer)                                  layer μ                                                                           a.sub.4                                                                              a.sub.4                                                                              a.sub.4                                                                              a.sub.4                                                                              a.sub.4                                            9      8      9      9      7                                         The seventh                                                                          (S layer)                                                                            (S layer)                                                                            (S layer)                                                                            (S layer)                                                                            (S layer)                                  layer μ                                                                           a.sub.7                                                                              a.sub.9                                                                              a.sub.11                                                                             a.sub.12                                                                             a.sub.13                                           9      8      9      9      7                                         Total  90     80     90     90     70                                         thickness                                                                     (μ)                                                                        __________________________________________________________________________    Layer                                                                         construction         Compara-                                                                             Compara-                                                                             Compara-                                   of raw film                                                                          29     30     tive 4 tive 5 tive 6                                     __________________________________________________________________________    The first                                                                            (S layer)                                                                            (S layer)                                                                            (SBC layer)                                                                          (SBC layer)                                                                          (H layer)                                  layer μ                                                                           a.sub.14                                                                             a.sub.15                                                                             M.sub.1                                                                              M.sub.1                                                                              H.sub.1                                            9      9     36     38      9                                         The second                                                                           (R layer)                                                                            (R layer)                                                                            (H layer)                                                                            (R layer)                                                                            (SBC layer)                                layer μ                                                                           a.sub.4                                                                              a.sub.4                                                                              H.sub.1                                                                              a.sub.4                                                                              M.sub.1                                            9      9     18     19     27                                         The third                                                                            (H layer)                                                                            (H layer)                                                                            (SBC layer)                                                                          (SBC layer)                                                                          (R layer)                                  layer μ                                                                           H.sub.1                                                                              H.sub.1                                                                              M.sub.1                                                                              M.sub.1                                                                              a.sub.4                                           18     18     36     38     18                                         The fourth                                                                           (SBC layer)                                                                          (SBC layer)                                                                          --     --     (SBC layer)                                layer μ                                                                           M.sub.17                                                                             M.sub.18             M.sub.1                                           18     18                   27                                         The fifth                                                                            (H layer)                                                                            (H layer)                                                                            --     --     (H layer)                                  layer μ                                                                           H.sub.1                                                                              H.sub.1              H.sub.1                                           18     18                    9                                         The sixth                                                                            (R layer)                                                                            (R layer)                                                                            --     --     --                                         layer μ                                                                           a.sub.4                                                                              a.sub.4                                                                 9      9                                                              The seventh                                                                          (S layer)                                                                            (S layer)                                                                            --     --     --                                         layer μ                                                                           a.sub.14                                                                             a.sub.15                                                                9      9                                                              Total  90     90     90     95     90                                         thickness                                                                     (μ)                                                                        __________________________________________________________________________

The marks in Table 9 indicate the following resins or resincompositions.

a₁₁ : EMA [Ethylene-methyl acrylate copolymer; content of methylacrylate: 18% by weight; MI: 2.0; mp: 96° C.; VSP: 60° C.]

a₁₂ : EBA [Ethylene-butyl acrylate copolymer; content of butyl acrylate:19% by weight; MI: 2.0; mp: 96° C.; VSP: 55° C.]

a₁₃ : EMAA [Ethylene-methacrylic acid copolymer; content of methacrylicacid: 9% by weight; MI: 3.0; mp: 98° C.; VSP: 80° C.]

a₁₄ : Ionomer [Ethylene-methyl methacrylatemethacrylic acid copolymer ofNa neutralized type; content of methyl methacrylate: 4.0 mol %; contentof methacrylic acid: 2.6 mol %; saponification degree: 40%; MI: 1.0;neutralization degree: 25%, mp: 83° C.; VSP: 64° C.]

a₁₅ : 1,2-polybutadiene [crystallinity: 25%; 1,2 bond: 92%; MI: 3.0(150° C.); density: 0.909 g/cm³ ; VSP: 68° C.]

M₁₃ : EVA (a₁): 35% by weight; linear low-density polyethylene (a₃): 20%by weight; EEA (a₉): 10% by weight; elastomer (b₁): 20% by weight; IPP(c₁): 10% by weight; PB-1 (c₂): 5% by weight.

M₁₄ : EVA (a₁): 35% by weight; linear low-density polyethylene (a₃): 20%by weight; EMA (a₁₁): 10% by weight; elastomer (b₁): 20% by weight; IPP(c₁): 10% by weight; PB-1 (c₂): 5% by weight.

M₁₅ : EVA (a₁): 35% by weight; linear low-density polyethylene (a₃): 20%by weight; EBA (a₁₂): 10% by weight; elastomer (b₁): 20% by weight; IPP(c₁): 10% by weight; PB-1 (c₂): 5% by weight.

M₁₆ : EVA (a₁): 35% by weight; linear low-density polyethylene (a₃): 20%by weight; EMAA (a₁₃): 10% by weight; elastomer (b₁): 20% by weight; IPP(c₁): 10% by weight; PB-1 (c₂): 5% by weight.

M₁₇ : EVA (a₁): 35% by weight; linear low-density polyethylene (a₃): 20%by weight; ionomer (a₁₄): 10% by weight; elastomer (b₁): 20% by weight;IPP (c₁): 10% by weight; PB-1 (c₂): 5% by weight.

M₁₈ : EVA (a₁): 35% by weight; linear low-density polyethylene (a₃): 20%by weight; 1,2-polybutadiene (a₁₅): 10% by weight; elastomer (b₁): 20%by weight; IPP (c₁): 10% by weight; PB-1 (c₂): 5% by weight.

                                      TABLE 10                                    __________________________________________________________________________                  Run No.                                                                                                      Compara-                                                                            Compara-                                                                            Compara-             Characteristics                                                                        unit 24  25   26  27   28  29   30  tive 4                                                                              tive                                                                                tive                 __________________________________________________________________________                                                             6                    Haze     %      0.7                                                                               0.6                                                                                0.9                                                                               1.0                                                                                1.0                                                                               0.8                                                                                0.7                                                                               1.8   1.9    0.5               Gloss × 6                                                                        %    140 150  145 140  140 140  140 90    90    145                  80° C. shrinkage                                                                %    38  36   34  32   38  33   39  34    32     30                  Tensile break                                                                          Kg/mm.sup.2                                                                          16.1                                                                              16.2                                                                               16.1                                                                              16.4                                                                               16.8                                                                              16.1                                                                               16.4                                                                              15.4                                                                                13.4                                                                                15.8               strength                                                                      Tensile break                                                                          %    230 240  210 210  220 250  270 260   220   220                  elongation                                                                    Stress at 100%                                                                         g/cm 830/                                                                              760/ 840/                                                                              860/ 660/                                                                              820/ 840/                                                                              890/  880/    890/               elongation                                                                             width                                                                              210 190  260 240  185 240  240 240   240   230                  (length direction/                                                            width direction)                                                              Sealing  °C.                                                                         78  75   80  76   81  78   76  120   98    156                  temperature                                                                   Heat resisting                                                                         °C.                                                                         157 158  155 151  159 151  152 145   110   153                  temperature                                                                   Anti-fogging                                                                           --   ⊚                                                                  ⊚                                                                   ⊚                                                                  ⊚                                                                   ⊚                                                                  ∘                                                                      ⊚                                                                  Δ                                                                             Δ                                                                             X                    property                                                                      Sealability                                                                            --   ⊚                                                                  ⊚                                                                   ⊚                                                                  ⊚                                                                   ⊚                                                                  ⊚                                                                   ⊚                                                                  ∘                                                                       X     X                    Tear strength                                                                          g    34  28   37  35   30  31   30   3     5     6                   Thickness of film                                                                      μ 10   9   10  10    8  10   10  10    10     10                  __________________________________________________________________________

EXAMPLE 6

Films of Run Nos. 31-38 and Comparative Run Nos. 7-14 are prepared inthe same manner as in Example 1 except that composition, constructionand ratio of thickness of the layers in Run No. 1 of Example 1 arechanged as shown in Table 11. However, the heat setting stabilizationtreatment after stretching is conducted by blowing air of 60° C. to thefilms to shrink by 15% in length direction and by 40% in width directionfor Run Nos. 31, 32, 34, 35 and 38 and Comparative Run Nos. 7, 8, 9, 10,11 and 14 and blowing air of 50° C. to the films to shrink by 10% inlength direction and by 30% in width direction for Run Nos. 33, 36 and37 and Comparative Run Nos. 12 and 13. The characteristics of the thusobtained films are shown in Table 12.

When ratio of thickness of S layer is less than 5% (Comparative Run No.7), transparency decreases as compared with the films of the presentinvention (Run Nos. 31 and 32) and is especially deteriorated duringshrinking in the tunnel and besides, anti-fogging property andsealability also deteriorate. Furthermore, when ratio of thickness of Slayer exceeds 40% (Comparative Run No. 8), tear strength decreased andstiffness also decreased and rigidity is lost.

When ratio of thickness of R layer is less than 5% (Comparative Run No.9), sealability somewhat deteriorated as compared with the films of thepresent invention (Run Nos. 33 and 34) and besides, tear strengthsharply reduces to cause break in wrapping a content having projections.When ratio of thickness exceeds 45% (Comparative Run No. 10),anti-fogging property deteriorates to a large extent.

When ratio of thickness of H layer is less than 5% (Comparative Run No.11), heat resisting temperature in sealing greatly lowers as comparedwith the films of the present invention (Run Nos. 35 and 36), stiffnessalso decreased, rigidity is lost and the film becomes difficult to beset on wrapping machines. When ratio of thickness exceeds 60%(Comparative Run No. 12), stretchability and tear strength deteriorate.

When ratio of thickness of SBC layer is less than 20% (Comparative RunNo. 13), the film is cold stretched with difficulty and many puncturesof bubble occurs and both transparency and tensile strength deteriorateas compared with the films of the present invention (Run Nos. 37 and38). When the ratio of thickness exceeds 80% (Comparative Run No. 14),tear strength decreases and stiffness greatly reduces and it becomesdifficult to set the film on wrapping machine.

                                      TABLE 11                                    __________________________________________________________________________            Run No.                                                                                       Com-                                                                              Com-                                                                              Com-                                                                              Com-                                                                              Com-                                                                              Com-                                                                              Com-                                                                              Com-                      Proportion              para-                                                                             para-                                                                             para-                                                                             para-                                                                             para-                                                                             para-                                                                             para-                                                                             para-                     of layers of            tive                                                                              tive                                                                              tive                                                                              tive                                                                              tive                                                                              tive                                                                              tive                                                                              tive                      raw film                                                                              31                                                                              32                                                                              33                                                                              34                                                                              35                                                                              36                                                                              37                                                                              38                                                                              7   8   9   10  11  12  13  14                        __________________________________________________________________________    The first                                                                              3                                                                              20                                                                              10                                                                               5                                                                              10                                                                              10                                                                              10                                                                              10                                                                               2  25  10  10  10   7  10  3                         layer                                                                         (S layer) %                                                                   The second                                                                            12                                                                              10                                                                               5                                                                              20                                                                              10                                                                              10                                                                              15                                                                               5                                                                              10  10   2  25  10   3  20  3                         layer                                                                         (R layer) %                                                                   The third                                                                              5                                                                               5                                                                              20                                                                               5                                                                               3                                                                              20                                                                              15                                                                               5                                                                               5   5   5   5   2  31  13  3                         layer                                                                         (H layer) %                                                                   The forth                                                                             60                                                                              30                                                                              30                                                                              40                                                                              54                                                                              20                                                                              20                                                                              60                                                                              66  20  66  20  56  18  15  85                        layer                                                                         (SBC layer) %                                                                 The fifth                                                                              5                                                                               5                                                                              20                                                                               5                                                                               3                                                                              20                                                                              15                                                                               5                                                                               5   5   5   5   2  31  12  2                         layer                                                                         (H layer) %                                                                   The sixth                                                                             12                                                                              10                                                                               5                                                                              20                                                                              10                                                                              10                                                                              15                                                                               5                                                                              10  10   2  25  10   3  20  2                         layer                                                                         (R layer) %                                                                   The seventh                                                                            3                                                                              20                                                                              10                                                                               5                                                                              10                                                                              10                                                                              10                                                                              10                                                                               2  25  10  10  10   7  10  2                         layer                                                                         (S layer) %                                                                   Total   70                                                                              70                                                                              90                                                                              70                                                                              70                                                                              90                                                                              90                                                                              70                                                                              70  70  70  70  70  90  90  70                        thickness                                                                     (μ)                                                                        __________________________________________________________________________

                                      TABLE 12                                    __________________________________________________________________________                     Run No.                                                      Characteristics                                                                            unit                                                                              31  32  33  34  35  36   37  38                              __________________________________________________________________________    Haze         %     0.9                                                                               0.6                                                                               0.6                                                                               0.7                                                                               0.7                                                                               0.8                                                                                0.6                                                                               0.7                           80° C. shrinkage                                                                    %   36  35  38  38  34  37   39  34                              Tensile break strength                                                                     Kg/mm.sup.2                                                                         11.5                                                                              10.2                                                                              15.8                                                                              10.6                                                                              10.7                                                                              15.8                                                                               15.2                                                                              9.3                           Tensile break elongation                                                                   %   320 310 230 310 320 240  260 370                             Stress at 100% elongation                                                                  g/cm                                                                              270/                                                                              260/                                                                              850/                                                                              270/                                                                              260/                                                                              840/ 760/                                                                              240/                            (length direction/                                                                         width                                                                             140 150 260 130 120 270  250 130                             width direction)                                                              Stress at 200% elongation                                                                  g/cm                                                                              580/                                                                              570/                                                                               --/                                                                              570/                                                                              530/                                                                               --/  --/                                                                              540/                            (length direction/                                                                         width                                                                             330 310 560 350 320 570  560 300                             width direction)                                                              Sealing temperature                                                                        °C.                                                                        86  85  85  87  86  87   85  86                              Heat resisting temperature                                                                 °C.                                                                        150 150 156 152 148 157  155 151                             Anti-fogging property                                                                      --  ⊚                                                                  ⊚                                                                  ⊚                                                                  ∘                                                                     ⊚                                                                  ⊚                                                                   ⊚                                                                  ⊚                Sealability  --  ∘                                                                     ⊚                                                                  ⊚                                                                  ∘                                                                     ∘                                                                     ⊚                                                                   ⊚                                                                  ⊚                Tear strength                                                                              g   45  43  20  74  43  47   57  40                              Stiffness    mg  22  20  42  34  18  45   41  21                              Thickness of film                                                                          μ                                                                              10  10  10  10  10  10   10  10                              __________________________________________________________________________                     Run No.                                                                       Com-                                                                              Com-                                                                              Com-                                                                              Com-                                                                              Com-                                                                              Com- Com-                                                                              Com-                                             para-                                                                             para-                                                                             para-                                                                             para-                                                                             para-                                                                             para-                                                                              para-                                                                             para-                                            tive                                                                              tive                                                                              tive                                                                              tive                                                                              tive                                                                              tive tive                                                                              tive                            Characteristics                                                                            unit                                                                              7   8   9   10  11  12   13  14                              __________________________________________________________________________    Haze         %     1.2                                                                               0.8                                                                               0.6                                                                               0.8                                                                               0.7                                                                               0.7                                                                                2.1                                                                               1.1                           80° C. shrinkage                                                                    %   38  35  34  23  38  38   39  33                              Tensile break strength                                                                     Kg/mm.sup.2                                                                         10.8                                                                              9.6                                                                               9.8                                                                               13.5                                                                              8.2                                                                               16.4                                                                               15.8                                                                              7.9                           Tensile break elongation                                                                   %   310 300 330 200 310 180  270 320                             Stress at 100% elongation                                                                  g/cm                                                                              290/                                                                              270/                                                                              250/                                                                              670/                                                                              230/                                                                              1000/                                                                              800/                                                                              210/                            (length direction/                                                                         width                                                                             150 130 140 240 110 400  250 100                             width direction)                                                              Stress at 200% elongation                                                                  g/cm                                                                              590/                                                                              570/                                                                              570/                                                                               --/                                                                              510/                                                                               --/  --/                                                                              500/                            (length direction/                                                                         width                                                                             340 320 330 510 290 --   530 210                             width direction)                                                              Sealing temperature                                                                        °C.                                                                        90  87  88  90  86  86   88  87                              Heat resisting temperature                                                                 °C.                                                                        151 150 149 150 120 157  151 135                             Anti-fogging property                                                                      --  Δ                                                                           ⊚                                                                  ∘                                                                     X   ⊚                                                                  ⊚                                                                   ∘                                                                     Δ                         Sealability  --  Δ                                                                           ∘                                                                     Δ                                                                           ∘                                                                     X   ⊚                                                                   ⊚                                                                  Δ                         Tear strength                                                                              g   40  17   8  70  24   7   63   7                              Stiffness    mg  19   8   6  27   4  40   38   3                              Thickness of film                                                                          μ                                                                              10  10  10  10  10  10   10  10                              __________________________________________________________________________

EXAMPLE 7

Raw films having a thickness of 90μ of Run Nos. 39-44 and ComparativeRun Nos. 15-20 are prepared in the same manner as in preparation of RunNo. 1 in Example 1 except that composition of SBC layer is changed asshown in Table 13.

These films are subjected to the same cold stretching as of Run No. 1 inExample 1. The films of Run Nos. 39-44 could be stably stretched withoutcausing punctures. On the other hand, the films of Comparative Run Nos.15-18 and 20 are inferior in bubble stability and especially, in thecase of Comparative Run No. 20, only the film having many streaks couldbe obtained. Furthermore, the raw film of Comparative Run No. 19 couldnot be cold stretched and when stretching temperature is graduallyraised, a bubble could be produced at 115° C., but is unstable andpunctured. Furthermore, transparency of the film is also inferior.Moreover, a raw film (Comparative Run No. 21) of 90μ thick having aconstruction of S/R/H/R/S which corresponds to the layer construction ofRun No. 1 except that the fourth layer (SBC layer) is omitted isprepared and cold stretching of this film is attempted, but could not beaccomplished like Comparative Run No. 19. The film could be stretched athigh temperature (120° C.), but puncture immediately occurs and the filmis inferior in stability and the desired film could not be obtained.

Characteristics of the resulting films are shown in Table 14.

The films of the present invention are superior to the comparative filmsin all of the characteristics and especially excellent inlow-temperature shrinkability and are wide in the range of sealingtemperature and excellent in tear strength and thus can be used as filmsfor shrink wrapping.

                                      TABLE 13                                    __________________________________________________________________________             Run No.                                                                                   Com-                                                                              Com-                                                                              Com-                                                                              Com-                                                                              Com-                                                                              Com-                                                      para-                                                                             para-                                                                             para-                                                                             para-                                                                             para-                                                                             para-                                                     tive                                                                              tive                                                                              tive                                                                              tive                                                                              tive                                                                              tive                                          39                                                                              40                                                                              41                                                                              42                                                                              43                                                                              44                                                                              15  16  17  18  19  20                                   __________________________________________________________________________    SBC                                                                              A     a.sub.1                                                                         --                                                                              a.sub.1                                                                         a.sub.1                                                                         --                                                                              --                                                                              a.sub.1                                                                           a.sub.1                                                                           --  --  a.sub.1                                                                           a.sub.1                              layer                                                                            component                                                                           70  35                                                                              92    98   5          70  10                                      B     b.sub.1                                                                         b.sub.1                                                                         b.sub.1                                                                         b.sub.1                                                                         b.sub.1                                                                         b.sub.1                                                                         b.sub.1                                                                           b1  b.sub.1                                                                           b.sub.1                                                                           --  b.sub.1                                 component                                                                           30                                                                              40                                                                              65                                                                               8                                                                              80                                                                              50                                                                               2  95  20  95      15                                      C     --                                                                              c.sub.1                                                                         --                                                                              --                                                                              c.sub.1                                                                         c.sub.1                                                                         --  --  c.sub.1                                                                           c.sub.1                                                                           c.sub.1                                                                           c.sub.1                                 component                                                                             60    20                                                                              50        80   5  30  75                                   __________________________________________________________________________

                                      TABLE 14                                    __________________________________________________________________________                      Run No.                                                     Characteristics                                                                            unit 39   40   41   42   43   44                                 __________________________________________________________________________    Haze         %      0.7                                                                                0.6                                                                                0.6                                                                                0.8                                                                                0.6                                                                                0.6                              80° C. shrinkage                                                                    %    39   37   36   35   33   35                                 Tensile break strength                                                                     Kg/mm.sup.2                                                                          15.7                                                                               16.4                                                                               15.3                                                                               14.2                                                                               16.3                                                                               16.5                             Tensile break elongation                                                                   %    230  220  230  240  240  220                                Stress at 100% elongation                                                                  g/cm 850/ 880/ 830/ 810/ 820/ 890/                               (length direction/                                                                         width                                                                              220  320  230  220  230  260                                width direction)                                                              Stress at 200% elongation                                                                  g/cm  --/  --/  --/  --/  --/  --/                               (length direction/                                                                         width                                                                              540  650  500  600  560  590                                width direction)                                                              Sealing temperature                                                                        °C.                                                                         87   87   88   86   87   87                                 Heat resisting temperature                                                                 °C.                                                                         156  158  152  153  159  161                                Anti-fogging property                                                                      --   ⊚                                                                   ⊚                                                                   ⊚                                                                   ⊚                                                                   ⊚                                                                   ⊚                   Sealability  --   ⊚                                                                   ⊚                                                                   ⊚                                                                   ⊚                                                                   ⊚                                                                   ⊚                   Tear strength                                                                              g    25   23   27   23   27   25                                 Stiffness    mg   44   52   50   41   52   58                                 Thickness of film                                                                          μ 10   10   10   10   10   10                                 __________________________________________________________________________                      Run No.                                                                       Compara-                                                                            Compara-                                                                            Compara-                                                                            Compara-                                                                            Compara-                                              tive  tive  tive  tive  tive                                Characteristics                                                                            unit 15    16    17    18    19                                  __________________________________________________________________________    Haze         %      2.3   1.7   1.8   2.2   6.5                               80° C. shrinkage                                                                    %    20    33    23    35    18                                  Tensile break strength                                                                     Kg/mm.sup.2                                                                          6.1   7.4   8.5   6.2   7.5                               Tensile break elongation                                                                   %    83    95    86    91    79                                  Stress at 100% elongation                                                                  g/cm  --/   --/   --/   --/   --/                                (length direction/                                                                         width                                                                              --    240   --    --    --                                  width direction)                                                              Stress at 200% elongation                                                                  g/cm  --/   --/   --/   --/   --/                                (length direction/                                                                         width                                                                              --    --    --    --    --                                  width direction)                                                              Sealing temperature                                                                        °C.                                                                         86    87    88    87    86                                  Heat resisting temperature                                                                 °C.                                                                         153   149   158   150   157                                 Anti-fogging property                                                                      --   Δ                                                                             ⊚                                                                    ∘                                                                       ∘                                                                       ∘                       Sealability  --   ∘                                                                       ∘                                                                       ∘                                                                       ∘                                                                       Δ                             Tear strength                                                                              g    13    11     8    16     8                                  Stiffness    mg   37    25    49    21    46                                  Thickness of film                                                                          μ 12    13    12    11    11                                  __________________________________________________________________________

EXAMPLE 8

Raw films (Run Nos. 45-51) of 70μ thick and of 5 to 8 layers in whichcompositions of S layer, SBC layer, R layer and H layer and constructionof the layers are as shown in Table 15 are prepared. Stretching isconducted in the same manner as in Run No. 8 of Example 1 to obtainfilms as shown in Table 16.

The resulting films are excellent in all of the characteristics and itis clarified that especially tear strength and stiffness (rigidity offilm) are highly improved in the films comprising at least 7 layers inwhich two R layers and two H layers are respectively arranged insymmetric positions than in the films of 5 layers or 6 layers.

Tray wrapping is carried out with the resulting films by the sameautomatic wrapping machine for stretch wrapping (elevator type) as usedin Example 1 and as a result, wrappings of good finish and good sealingby hot plate could be obtained without occurrence of creases.

                                      TABLE 15                                    __________________________________________________________________________    Layer                                                                         construc-                                                                     tion of                                                                              Run No.                                                                raw film                                                                             45     46     47     48     49     50     51                           __________________________________________________________________________    The first                                                                            (S layer)                                                                            (S layer)                                                                            (S layer)                                                                            (S layer)                                                                            (S layer)                                                                            (S layer)                                                                            (S layer)                    layer  a.sub.2                                                                              a.sub.2                                                                              a.sub.2                                                                              a.sub.2                                                                              a.sub.2                                                                              a.sub.2                                                                              a.sub.2                      μ    7     7      7      7      7      7       7                           The second                                                                           (R layer)                                                                            (SBC layer)                                                                          (R layer)                                                                            (H layer)                                                                            (R layer)                                                                            (H layer)                                                                            (SBC layer)                  layer  a.sub.3                                                                              M.sub.1                                                                              a.sub.3                                                                              H.sub.2                                                                              a.sub.3                                                                              H.sub.2                                                                              M.sub.1                      μ   24     21     5      3      7      4      14                           The third                                                                            (H layer)                                                                            (R layer)                                                                            (SBC layer)                                                                          (R layer)                                                                            (H layer)                                                                            (R layer)                                                                            (H layer)                    layer  H.sub.1                                                                              a.sub.3                                                                              M.sub.1                                                                              a.sub.3                                                                              H.sub.1                                                                              a.sub.3                                                                              H.sub.1                      μ    7     7      20     5      3      3       4                           The forth                                                                            (SBC layer)                                                                          (H layer)                                                                            (H layer)                                                                            (SBC layer)                                                                          (R layer)                                                                            (SBC layer)                                                                          (SBC layer)                  layer  M.sub.1                                                                              H.sub. 1                                                                             H.sub.1                                                                              M.sub.1                                                                              a.sub.3                                                                              M.sub.1                                                                              M.sub.1                      μ   25     7      7      40     5      17     10                           The fifth                                                                            (S layer)                                                                            (SBC layer)                                                                          (SBC layer)                                                                          (R layer)                                                                            (SBC layer)                                                                          (H layer)                                                                            (R layer)                    layer  a.sub.2                                                                              M.sub.1                                                                              M.sub.1                                                                              a.sub.3                                                                              M.sub.1                                                                              H.sub.2                                                                              a.sub.3                      μ    7     21     20     4      30     7      11                           The sixth                                                                            --     (S layer)                                                                            (R layer)                                                                            (H layer)                                                                            (H layer)                                                                            (SBC layer)                                                                          (H layer)                    layer         a.sub.2                                                                              a.sub.3                                                                              H.sub.2                                                                              H.sub.1                                                                              M.sub.1                                                                              H.sub.1                      μ          7      4      4      4      18      3                           The seventh                                                                          --     --     (S layer)                                                                            (S layer)                                                                            (R layer)                                                                            (R layer)                                                                            (SBC layer)                  layer                a.sub.2                                                                              a.sub.2                                                                              a.sub.3                                                                              a.sub.3                                                                              M.sub.1                      μ                 7      7      7      7      14                           The eighth                                                                           --     --     --     --     (S layer)                                                                            (S layer)                                                                            (S layer)                    layer                              a.sub.2                                                                              a.sub.2                                                                              a.sub.2                      μ                               7      7       7                           Total  70     70     70     70     70     70     70                           thickness                                                                     (μ)                                                                        __________________________________________________________________________

                                      TABLE 16                                    __________________________________________________________________________                      Run No.                                                     Characteristics                                                                            unit 45   46   47   48   49   50   51                            __________________________________________________________________________    Haze         %    0.8  0.6  0.6  0.5  0.7  0.7  0.6                           80° C. shrinkage                                                                    %    35   33   35   37   36   37   34                            Tensile break strength                                                                     Kg/mm.sup.2                                                                        12.5 11.3 13.6 13.2 12.2 12.5 12.3                          Tensile break elongation                                                                   %    290  350  330  360  330  320  340                           Stress at 100% elongation                                                                  g/cm 330/170                                                                            320/160                                                                            300/150                                                                            290/150                                                                            260/140                                                                            280/160                                                                            270/180                       (length direction/                                                                         width                                                            width direction)                                                              Stress at 200% elongation                                                                  g/cm 610/310                                                                            590/300                                                                            580/300                                                                            570/300                                                                            550/290                                                                            580/280                                                                            530/270                       (length direction/                                                                         width                                                            width direction)                                                              Sealing temperature                                                                        °C.                                                                         86   86   87   88   86   87   86                            Heat resisting temperature                                                                 °C.                                                                         152  150  151  153  152  152  151                           Anti-fogging property                                                                      --   ⊚                                                                   ⊚                                                                   ⊚                                                                   ⊚                                                                   ⊚                                                                   ⊚                                                                   ⊚              Sealability  --   ⊚                                                                   ⊚                                                                   ⊚                                                                   ⊚                                                                   ⊚                                                                   ⊚                                                                   ⊚              Tear strength                                                                              g    63   55   61   82   92   86   65                            Stiffness    mg   28   25   20   40   33   34   24                            Thickness of film                                                                          μ 10   10   10   10   10   10   10                            __________________________________________________________________________

EXAMPLE 9

EVA (a₁): 50% by weight, linear low-density polyethylene (a₄): 10% byweight, ethylene-α-olefin copolymer thermoplastic elastomer (b₁): 25% byweight, IPP (c₁): 10% by weight and crystalline polybutene (c₂): 5% byweight are mixed and to 100 parts by weight of the resulting resinmixture are added 15 parts by weight of hydrogenated cyclopentadieneresin [softening point 125° C. measured by ring and ball method]: AS₁ asan AS agent and besides, 5 parts by weight of a mineral oil and thismixture is kneaded to obtain a specific mixed composition: (M₁₉) for SBClayer. Furthermore, IPP (c₁): 70% by weight and PB-1 (c₂): 30% by weightare mixed to obtain a mixed composition (H₁) for H layer. The linearlow-density polyethylene (a₄) is used for R layer and EVA (a₂) is usedfor S layer. In the same manner as in Example 1, raw films of 80, 90 and100μ thick (Run Nos. 52-54 in Table 17) are obtained from them usingfour extruders. These raw films are cold stretched to 3.2 times inlength direction and to 3.0 times in width direction in the same manneras in Example 1 except that they are heated to 35° C. and the stretchingterminated region is cooled to 10° C. and thereafter, are subjected toheat setting stabilization treatment in the same manner as in Example 1at a shrink of 10% in length direction and 30, 20 or 10% in widthdirection to obtain films having a final thickness of 10μ.Characteristics of the resulting films are shown in Table 18.

It can be seen that the films of Run Nos. 52-54 all has excellentcharacteristic values. Furthermore, when wrapping is conducted withthese films using no tunnel by the automatic wrapping machines forstretch packaging (pillow type and elevator type) used in Example 1,wrapping with no creases and good sealability could be accomplished byall of these films. Moreover, when hand wrapping is carried out withthese films by the aforementioned hand wrapper, wrapping in good finishcould be performed however, the film of Run No. 52 has the tendency toretain creases as compared with the film of Run No. 54 unless tensionapplied to the film is adjusted in wrapping by the wrapping machine.

When the raw film of Run No. 54 which is cold stretched is not subjectedto the heat setting stabilization treatment, this film having 10μ thickhas stresses in length direction/width direction of 1200/800 (g/cmwidth) at 200% elongation and many creases occurs in the above stretchwrapping and when the film is strongly pulled in order to remove thecreases, the tray is broken and wrapping could not be accomplished.

                  TABLE 17                                                        ______________________________________                                                      Run No.                                                                       52      53       54                                             ______________________________________                                        The first layer a.sub.2   a.sub.2  a.sub.2                                    (S layer)       8         9        10                                         μ                                                                          The second layer                                                                              a.sub.4   a.sub.4  a.sub.4                                    (R layer)       8         9        10                                         μ                                                                          The third layer H.sub.1   H.sub.1  H.sub.1                                    (H layer)       4         5        5                                          μ                                                                          The forth layer M.sub.19  M.sub.19 M.sub.19                                   (SBC layer)     40        45       50                                         μ                                                                          The fifth layer H.sub.1   H.sub.1  H.sub.1                                    (H layer)       4         4        5                                          μ                                                                          The sixth layer a.sub.4   a.sub.4  a.sub.4                                    (R layer)       8         9        10                                         μ                                                                          The seventh layer                                                                             a.sub.2   a.sub.2  a.sub.2                                    (S layer)       8         9        10                                         μ                                                                          Total thickness 80        90       100                                        (μ)                                                                        ______________________________________                                    

                  TABLE 18                                                        ______________________________________                                                       Run No.                                                        Characteristics                                                                           unit     52       53     54                                       ______________________________________                                        Haze        %        0.6      0.5    0.5                                      80° C. shrinkage                                                                   %        36       40     43                                       Tensile break                                                                             Kg/mm.sup.2                                                                            8.0      10.0   12.4                                     strength                                                                      Tensile break                                                                             %        360      320    290                                      elongation                                                                    Stress at 100%                                                                            g/cm     250/120  290/150                                                                              300/280                                  elongation  width                                                             (length direction/                                                            width direction)                                                              Stress at 200%                                                                            g/cm     470/200  520/240                                                                              420/370                                  elongation  width                                                             (length direction/                                                            width direction)                                                              Sealing     °C.                                                                             84       84     85                                       temperature                                                                   Heat resisting                                                                            °C.                                                                             150      150    150                                      temperature                                                                   Anti-fogging                                                                              --       ⊚                                                                       ⊚                                                                     ⊚                         property                                                                      Sealability --       ⊚                                                                       ⊚                                                                     ⊚                         Tear strength                                                                             g        42       35     24                                       Stiffness   mg       23       27     30                                       Thickness of film                                                                         μ     10       10     10                                       ______________________________________                                    

EXAMPLE 10

Raw films of Run Nos. 55-58 are prepared with the compositions ofrespective layers and the construction of the layers as shown in Table19 in the same manner as in Run No. 6 of Example 1. The raw films of RunNos. 55-56 are irradiated with 5 Mrad of electron rays (energy of 500KV) as energy beam and the raw film of Run No. 57 is irradiated with 3Mrad of the same electron rays. One side of the raw film of Run No. 58is irradiated with 5 Mrad of electron rays (150 KV) as energy beam.These films are subjected to the cold stretching and the heat settingstabilization treatment in the same manner as in Example 1 to obtain thefilms as shown in Table 20.

It can be seen that the films of Run Nos. 55-58 has excellentcharacteristics. Especially, heat resisting temperature in sealing canbe widened to the high temperature side without causing elevation ofinitiation temperature and the range of proper heat sealing temperaturecan be widened.

When wrapping is carried out with the films of Run Nos. 55-58 by thestretch wrapping machine used in Example 1, the wrapping could beperformed without creases and with a good finish.

                  TABLE 19                                                        ______________________________________                                        Layer                                                                         construc-                                                                     tion of  Run No.                                                              raw film 55        56        57      58                                       ______________________________________                                        The first                                                                              (S layer) (S layer) (S layer)                                                                             (S layer)                                layer    a.sub.16  a.sub.17 *.sup.2                                                                        a.sub.17                                                                              a.sub.2 *.sup.4                          μ     7         9         7       11                                       The second                                                                             (R layer) (R layer) (R layer)                                                                             (R layer)                                layer    a.sub.4   a.sub.4   a.sub.4 a.sub.4                                  μ     7         9         7       11                                       The third                                                                              (H layer) (H layer) (H layer)                                                                             (H layer)                                layer    H.sub.1   H.sub.1   H.sub.1 H.sub.1                                  μ     4         18        4       22                                       The forth                                                                              (SBC      (SBC      (SBC    (SBC                                     layer    layer)    layer)    layer)  layer)                                   μ     M.sub.1 *.sup.1                                                                         M.sub.1 *.sup.1                                                                         M.sub.18 *.sup.3                                                                      M.sub.1 *.sup.1                                   35        18        35      22                                       The fifth                                                                              (H layer) (H layer) (H layer)                                                                             (H layer)                                layer    H.sub.1   H.sub.1   H.sub.1 H.sub.1                                  μ     3         18        3       22                                       The sixth                                                                              (R layer) (R layer) (R layer)                                                                             (R layer)                                layer    a.sub.4   a.sub.4   a.sub.4 a.sub.4                                  μ     7         9         7       11                                       The seventh                                                                            (S layer) (S layer) (S layer)                                                                             (S layer)                                layer    a.sub.16  a.sub.17 *.sup.2                                                                        a.sub.17                                                                              a.sub.2 *.sup.5                          μ     7         9         7       11                                       Total    70        90        70      110                                      thickness                                                                     (μ)                                                                        ______________________________________                                         *.sup.1 Gel % and MI of SBC layer were 12% and 0.08, respectively.            *.sup.2 Gel % and MI of S layer were 2% and 0.6, respectively.                *.sup.3 Gel % and MI of SBC layer were 20% and 0.04, respectively.            *.sup.4 Gel % and MI of S layer were 10% and 0.1 (irradiated side),           respectively.                                                                 *.sup.5 Gel % and MI of S layer were 0% and 2.2, respectively.           

The marks in Table 19 indicate the following resin and resincomposition.

a₁₆ : EVA [Content of vinyl acetate group: 13% by weight; MI: 4.0; mp:93° C.; VSP: 75° C.]

a₁₇ : Composition prepared by kneading EVA (a₂) with 0.5% of anantioxidant.

                  TABLE 20                                                        ______________________________________                                                      Run No.                                                         Characteristics                                                                          unit     55      56     57    58                                   ______________________________________                                        Haze       %        0.6     0.6    0.6   0.8                                  80° C. shrinkage                                                                  %        37      38     37    35                                   Tensile break                                                                            Kg/mm.sup.2                                                                            12.7    16.3   10.1  9.3                                  strength                                                                      Tensile break                                                                            %        320     250    340   370                                  elongation                                                                    Stress at 100%                                                                           g/cm     340/    820/   310/  280/                                 elongation width    170     280    150   150                                  (length direction/                                                            width direction)                                                              Stress at 200%                                                                           g/cm     600/     --/   570/  560/                                 elongation width    310     550    310   290                                  (length direction/                                                            width direction)                                                              Sealing    °C.                                                                             92      86     84    90                                   temperature                                                                   Heat resisting                                                                           °C.                                                                             179     178    178   159                                  temperature                                                                   Anti-fogging                                                                             --       ⊚                                                                      ⊚                                                                     ⊚                                                                    ⊚                     property                                                                      Sealability                                                                              --       ⊚                                                                      ⊚                                                                     ⊚                                                                    ⊚                     Tear strength                                                                            g        57      34     52    73                                   Stiffness  mg       28      51     25    44                                   Thickness of film                                                                        μ     10      10     10    12                                   ______________________________________                                    

EXAMPLE 11

Raw films of Run Nos. 59-63 are prepared with the compositions ofrespective layers and the construction of the layers as shown in Table21 in the same manner as in Example 1. These raw films are coldstretched in the same manner as in Run No. 6 of Example 1 to obtainrespective films. However, heat setting stabilization treatment iscarried out with shrinking by 10% in length direction and 30% in widthdirection for the films of Run Nos. 59-61 and 15% in length and 40% inwidth direction for the films of Run Nos. 62-63. Characteristics of theresulting films are shown in Table 22.

The films of Run Nos. 59-63 are excellent in all of the characteristics.Especially, the films of the present invention such as the film of RunNo. 59 could be made to extremely thin film of 5μ thick and besides,even with such thickness, the films maintain excellent characteristicssuch as tensile strength, sealability (temperature range), tearstrength, and stiffness (rigidity of the film) by which the films can beused for shrink wrapping. The film of Run No. 62 has excellentcharacteristics such as stretchability, sealability (temperature range)and tear strength as extremely thin film for stretch wrapping.

The films of Run Nos. 59-61 are subjected to practical wrapping test inthe same manner as in Example 1 using the L type wrapping machine andthe commercially available shrinking tunnel and stretch wrapping machine(with a simple tunnel). As a result, tight and beautiful wrapping couldbe performed with a good finish and without occurrence of creases anddeterioration of optical characteristics after shrinking.

When the same wrapping as in Example 1 is carried out with the films ofRun Nos. 62-63 using the same stretch wrapping machine as used inExample 1, wrapping with no crease and with a good finish could beperformed with these films.

Thus, the films of the present invention can be sufficiently used forboth the shrink wrapping and the stretch wrapping even in the extremelythin thickness of 10μ or less and such films have never been able to beproduced up to the present.

In the case of hand wrapping, stretch wrapping could be performedsmoothly and without occurrence of break with the films of Run Nos. 59,60, 62 and 63.

                  TABLE 21                                                        ______________________________________                                                   Run No.                                                                       59    60      61      62    63                                     ______________________________________                                        The first layer                                                                            a.sub.2 a.sub.2 a.sub.2                                                                             a.sub.2                                                                             a.sub.2                              (S layer)    4       5       6     5     7                                    μ                                                                          The second layer                                                                           a.sub.4 a.sub.4 a.sub.4                                                                             a.sub.4                                                                             a.sub.4                              (R layer)    4       4       5     5     7                                    μ                                                                          The third layer                                                                            H.sub.2 H.sub.2 H.sub.2                                                                             H.sub.2                                                                             H.sub.1                              (H layer)    8       10      11    3     4                                    μ                                                                          The forth layer                                                                            M.sub.19                                                                              M.sub.19                                                                              M.sub.19                                                                            M.sub.19                                                                            M.sub.19                             (SBC layer)  8       9       11    25    35                                   μ                                                                          The fifth layer                                                                            H.sub.2 H.sub.2 H.sub.2                                                                             H.sub.2                                                                             H.sub.1                              (H layer)    8       10      11    2     3                                    μ                                                                          The sixth layer                                                                            a.sub.4 a.sub.4 a.sub.4                                                                             a.sub.4                                                                             a.sub.4                              (R layer)    4       4       5     5     7                                    μ                                                                          The seventh layer                                                                          a.sub.2 a.sub.2 a.sub.2                                                                             a.sub.2                                                                             a.sub.2                              (S layer)    4       5       6     5     7                                    μ                                                                          Total thickness                                                                            40      47      55    50    70                                   (μ)                                                                        ______________________________________                                    

                                      TABLE 22                                    __________________________________________________________________________                  Run No.                                                         Characteristics                                                                        unit 59   60   61   62   63                                          __________________________________________________________________________    Haze     %    0.4  0.5  0.5  0.7  0.6                                         80° C. shrinkage                                                                %    39   38   38   35   36                                          Tensile break                                                                          Kg/mm.sup.2                                                                        16.1 16.3 16.7 7.7  7.5                                         strength                                                                      Tensile break                                                                          %    210  230  220  290  330                                         elongation                                                                    Stress at 100%                                                                         g/cm 480/130                                                                            520/160                                                                            610/200                                                                            160/90                                                                             190/110                                     elongation                                                                             width                                                                (length direction/                                                            width direction)                                                              Stress at 200%                                                                         g/cm  --/290                                                                             --/280                                                                             --/390                                                                            330/190                                                                            400/220                                     elongation                                                                             width                                                                (length direction/                                                            width direction)                                                              Sealing  °C.                                                                         85   85   85   84   85                                          temperature                                                                   Heat resisting                                                                         °C.                                                                         152  155  157  151  150                                         temperature                                                                   Anti-fogging                                                                           --   ⊚                                                                   ⊚                                                                   ⊚                                                                   ⊚                                                                   ⊚                            property                                                                      Sealability                                                                            --   ∘                                                                      ∘                                                                      ⊚                                                                   ⊚                                                                   ⊚                            Tear strength                                                                          g    18   24   30   42   48                                          Stiffness                                                                              mg   25   32   39   19   28                                          Thickness of film                                                                      μ 5    6    7    8    10                                          __________________________________________________________________________

EXAMPLE 12

The raw films of Run No. 1 in Example 1 are subjected to cold stretchingand heat setting stabilization treatment in the same manner as inExample 1 with changing the stretching temperature to 40°, 53° and 80°C. to obtain films of Run Nos. 64-66.

All of the raw films could be stably stretched at any of the abovestretching temperatures with a little unevenness in thickness.Characteristics of the resulting films are shown in Table 23.

The resulting films are excellent in all of the characteristics and arewell balanced in transparency, tensile strength, sealability(temperature range), tear strength and stiffness (rigidity of thefilms). When the same shrink wrapping test as in Example 1 is conducted,the wrapping could be performed tightly, with no creases and with a goodfinish.

                  TABLE 23                                                        ______________________________________                                                       Run No.                                                        Characteristics                                                                          unit      64       65     66                                       ______________________________________                                        Haze       %         0.6      0.6    1.5                                      80° C. shrinkage                                                                  %         38       35     20                                       Tensile break                                                                            Kg/mm.sup.2                                                                             16.5     16.0   7.5                                      strength                                                                      Tensile break                                                                            %         230      240    180                                      elongation                                                                    Stress at 100%                                                                           g/cm      860/220  830/220                                                                              830/210                                  elongation width                                                              (length direction/                                                            width direction)                                                              Stress at 200%                                                                           g/cm       --/540   --/550                                                                               --/530                                  elongation width                                                              (length direction/                                                            width direction)                                                              Sealing    °C.                                                                              87       86     87                                       temperature                                                                   Heat resisting                                                                           °C.                                                                              155      155    155                                      temperature                                                                   Anti-fogging                                                                             --        ⊚                                                                       ⊚                                                                     ⊚                         property                                                                      Sealability                                                                              --        ⊚                                                                       ⊚                                                                     ⊚                         Tear strength                                                                            g         25       27     27                                       Stiffness  mg        46       45     46                                       Thickness of film                                                                        μ      10       10     10                                       ______________________________________                                    

EXAMPLE 13

A mixed composition (M₂₀) for SBC layer is prepared in the followingmanner. That is, 35% by weight of ethylene-vinyl acetate copolymer (a₁),30% by weight of a linear low-density polyethylene (a₁₈) [copolymer ofethylene with 20% by weight of octene-1 as α-olefin; MI: 3.0; VSP: 81°C.; mp: 115° C.; density: 0.907 g/cm³ ], 15% by weight of a softthermoplastic elastomer (b₁), 10% by weight of a crystallinepolypropylene (c₁) and 5% by weight of crystalline polybutene-1 (c₂) aremixed, and to 100 parts by weight of the mixed resins is added 10 partsby weight of a hydrogenated cyclopentadiene resin (AS₁) as an AS agentand the resulting mixture is kneaded. Next, a mixed composition (H₁) forH layer is prepared in the same manner as in Example 1. Furthermore,linear low-density polyethylene (a₁₈) is prepared as a resin for R layerand ethylene-vinyl acetate copolymer (a₂) is prepared as a resin for Slayer. These resins for SBC layer, H layer, R layer and S layer arethermoplasticized and melt mixed at a cylinder maximum temperature of220° C. by the following four extruders, respectively: an extruderhaving a screw of 50 mm in diameter (L/D=37) and an injection port atthe position of L/D=8 from the tip portion, an extruder having a screwof 40 mm in diameter (L/D=29), an extruder having a screw of 40 mm indiameter (L/D=37) and an injection port at the position of L/D=8 fromthe tip portion, and an extruder having a screw of 40 mm in diameter(L/D=37) and an injection port at the position of L/D=12 from the tipportion, In this case, from the injection ports of extruders for R layerand S layer, two anti-fogging agents of glycerin monooleate anddiglycerin monooleate are injected so that each of the layers containedthe anti-fogging agents in an amount of 1.5% by weight each and totally3.0% by weight of them and are kneaded with the above resins. Respectivekneaded products are extruded from an annular die (die slit: 1.0 mm)having 7 layers of 4 kinds and rapidly cooled by a water cooling ringprovided at the position of 5 cm from the tip of the die which uniformlydischarges water to obtain a raw film of 180 mmφ (Run No. 67 in Table24). Various raw films of Run Nos. 68-69 in Table 24 are obtained in thesame manner as above except that only the thickness is changed.

Unevenness (in circumferential direction) in thickness of the resultingraw films is within ±2%. Each of these raw films is passed between twopairs of carrying nip rolls and take-off nip rolls, where the films areheated to 65° C. by hot air and then air is introduced into the films asthey are and the films are continuously inflated by the rectificationcontact guide to stretch them to about 3.2-3.6 times in length directionand about 3.2-3.7 times in width direction. The stretching terminatedportion is cooled by an air ring from which cold air of 18° C. isjetted, folded by a deflator, and taken off by nip rolls and air of 50°C. is blown against the film and the film is shrunk by 12% in lengthdirection and by 30% in width direction in a zone between two pairs ofinlet nip rolls and outlet nip rolls, speed of the latter being slower15% than that of the former. Thereafter, the film is subjected to heatsetting stabilization treatment simultaneously with orientationmodification and edge portions of the film are slit to separate into twofilms, which are respectively wound up under a constant tension toobtain desired films having a given thickness. Similarly, the films ofthe given thickness are obtained using raw films having the compositionsand the construction of layers of Comparative Run Nos. 22-26 shown inTable 24 (3.0% by weight of the anti-fogging agent (same as used in RunNos. 67-69) was injected into SBC layer and S layer in Comparative RunNos. 22-26. Characteristics of the resulting film are shown in Table 25.The films of Run Nos. 67-69 are all excellent in stretchability andespecially, even in the case of final thickness of 5μ of Run No. 67, thefilm could be very stably performed with two punctures of bubble per 1hour. On the other hand, film could be formed in Comparative Run No. 22,but many punctures, namely, 35 punctures occurred per 1 hour and filmformation could not be stably performed.

The films of Run Nos. 67-69 are excellent in all of the characteristicsand especially high in tear strength and it is a surprising effect thateven the extremely thin film of 5μ showed a value of 170 g. Moreover,they have high stiffness which shows the rigidity of the film and aresuperior in running properties on wrapping machine.

A lump of meat put on a PSP tray is wrapped with each of the films inTable 25 by the wrapping machine for stretch wrapping used in Example 1.When the films of Run Nos. 67-69 are used, good wraps are obtained evenby loose wrapping in case a simple tunnel which discharges a hot air of80° C. is positioned above the sealing part of the wrapping machine.

When objects having sharp projections such as frozen lobsters and frozenfishes are wrapped, break does not occur or does not propagate even ifit occurs in case of using the films of Run Nos. 67-69, although breaksoccur frequently in case of conventional films. With reference to thefilms of Comparative Run Nos. 22-26, objects having no projections couldbe satisfactorily wrapped with the films of Comparative Run Nos. 24 and26 only when the objects are loosely wrapped using a simple tunnel whilethe objects could not be satisfactorily wrapped with the occurrence ofmany breaks in the case of using the films of Comparative Run Nos. 22,23 and 25. Furthermore, when objects having projections are wrapped,many breaks occurs in all of the films of Comparative Run Nos. 22-26 andthey propagate and thus, satisfactory wraps could not be obtained.

As explained above, the films of the present invention have far moresuperior features than conventional films in the conventional use ofshrink films and especially, even when the films are made to extremelythin films as compared with conventional films, such extremely thinfilms maintain sufficient practical characteristics.

                  TABLE 24                                                        ______________________________________                                        Layer    Run No.                                                              construc-                            Compara-                                 tion of                              tive                                     raw film 67        68        69      22                                       ______________________________________                                        The first                                                                              (S layer) (S layer) (S layer)                                                                             (S layer)                                layer    a.sub.2   a.sub.2   a.sub.2 a.sub.2                                  μ     4         5         6       4                                        The second                                                                             (R layer) (R layer) (R layer)                                                                             (SBC layer)                              layer    a.sub.18  a.sub.18  a.sub.18                                                                              M.sub.5                                  μ     4         5         6       8                                        The third                                                                              (H layer) (H layer) (H layer)                                                                             (H layer)                                layer    H.sub.1   H.sub.1   H.sub.1 H.sub.1                                  μ     8         10        12      16                                       The forth                                                                              (SBC      (SBC      (SBC    (SBC                                     layer    layer)    layer)    layer)  layer)                                   μ     M.sub.20  M.sub.20  M.sub.20                                                                              M.sub.5                                           8         10        12      8                                        The fifth                                                                              (H layer) (H layer) (H layer)                                                                             (S layer)                                layer    H.sub.1   H.sub.1   H.sub.1 a.sub.2                                  μ     8         10        12      4                                        The sixth                                                                              (R layer) (R layer) (R layer)                                                                             --                                       layer    a.sub.18  a.sub.18  a.sub.18                                         μ     4         5         6                                                The seventh                                                                            (S layer) (S layer) (S layer)                                                                             --                                       layer    a.sub.2   a.sub.2   a.sub.2                                          μ     4         5         6                                                Total    40        50        60      40                                       thickness                                                                     (μ)                                                                        ______________________________________                                        Layer    Run No.                                                              construc-                                                                              Compara-  Compara-  Compara-                                                                              Compara-                                 tion of  tive      tive      tive    tive                                     raw film 23        24        25      26                                       ______________________________________                                        The first                                                                              (S layer) (S layer) (S layer)                                                                             (S layer)                                layer    a.sub.2   a.sub.2   a.sub.2 a.sub.2                                  μ     5         6         5       6                                        The second                                                                             (SBC      (SBC      (SBC    (SBC                                     layer    layer)    layer)    layer)  layer)                                   μ     M.sub.5   M.sub.5   M.sub.5 M.sub.5                                           10        12        5       6                                        The third                                                                              (H layer) (H layer) (H layer)                                                                             (H layer)                                layer    H.sub.1   H.sub.1   H.sub.1 H.sub.1                                  μ     20        24        10      12                                       The forth                                                                              (SBC      (SBC      (SBC    (SBC                                     layer    layer)    layer)    layer)  layer)                                   μ     M.sub.5   M.sub.5   M.sub.5 M.sub.5                                           10        12        10      12                                       The fifth                                                                              (S layer) (S layer) (H layer)                                                                             (H layer)                                layer    a.sub.2   a.sub.2   H.sub.1 H.sub.1                                  μ     5         6         10      12                                       The sixth                                                                              --        --        (SBC    (SBC                                     layer                        layer)  layer)                                   μ                         M.sub.5 M.sub.5                                                               5       6                                        The seventh                                                                            --        --        (S layer)                                                                             (S layer)                                layer                        a.sub.2 a.sub.2                                  μ                         5       6                                        Total    50        60        50      60                                       thickness                                                                     (μ)                                                                        ______________________________________                                    

                                      TABLE 25                                    __________________________________________________________________________                  Run No.                                                                                   Compara-                                                                            Compara-                                                                            Compara-                                                                            Compara-                                                                            Compara-                                              tive  tive  tive  tive  tive                        Characteristics                                                                        unit 67  68  69  22    23    24    25    26                          __________________________________________________________________________    Haze     %    0.4 0.4 0.5 0.5   0.6   0.6   0.5   0.6                         80° C. shrinkage                                                                %    39  39  38  38    38    37    38    38                          Tensile break                                                                          Kg/mm.sup.2                                                                        18.2                                                                              18.0                                                                              18.2                                                                              12.0  12.5  12.7  12.0  12.6                        strength                                                                      Tensile break                                                                          %    220 210 220 200   210   200   200   200                         elongation                                                                    Stress at 100%                                                                         g/cm 410/                                                                              600/                                                                              800/                                                                              360/  530/  750/  580/  760/                        elongation                                                                             width                                                                              190 200 250 150   250   330   200   320                         (length direction/                                                            width direction)                                                              Stress at 200%                                                                         g/cm  --/                                                                               --/                                                                               --/                                                                               --/   --/   --/   --/   --/                        elongation                                                                             width                                                                              310 450 600 300   460   750   510   740                         (length direction/                                                            width direction)                                                              Sealing  °C.                                                                         90  90  90  89    90    89    90    90                          temperature                                                                   Heat resisting                                                                         °C.                                                                         158 156 156 155   157   157   157   158                         temperature                                                                   Anti-fogging                                                                           --   ⊚                                                                  ⊚                                                                  ⊚                                                                  ∘                                                                       ⊚                                                                    ⊚                                                                    ⊚                                                                    ⊚            property                                                                      Sealability                                                                            --   ⊚                                                                  ⊚                                                                  ⊚                                                                  ⊚                                                                    ⊚                                                                    ⊚                                                                    ⊚                                                                    ⊚            Tear strength                                                                          g    180 170 170 3     4     4     7     10                          Stiffness                                                                              mg   25  33  45  4     8     13    24    30                          Thickness of film                                                                      μ 5   7   10  5     7     10    7     10                          Stretchability*                                                                             ∘                                                                     ⊚                                                                  ⊚                                                                  x     Δ                                                                             ∘                                                                       Δ                                                                             ∘               __________________________________________________________________________        ⊚:                                                               The number of punctures of bubble (per 1 hour)                                1 or less                                                                   ∘:                                                                  The number of punctures of bubble (per 1 hour)                                2-5                                                                     *   Δ:                                                                        The number of punctures of bubble (per 1 hour)                                6-15                                                                        x:                                                                              The number of punctures of bubble (per 1 hour)                                16 or more                                                          

EXAMPLE 14

A mixed composition (M₂₁) for SBC layer is prepared in the followingmanner. That is, 35% by weight of ethylene-vinyl acetate copolymer (a₁),30% by weight of a linear low-density polyethylene (a₁₉) [copolymer ofethylene with 15% by weight of hexene-1 as α-olefin; MI: 3.6; VSP: 82°C.; mp: 117° C.; density: 0.908 g/cm³ ], 25% by weight of a softthermoplastic elastomer (b₁), 5% by weight of a crystallinepolypropylene (c₁) and 5% by weight of crystalline polybutene-1 (c₂) aremixed, and to 100 parts by weight of the mixed resins is added 10 partsby weight of a hydrogenated cyclopentadiene resin (AS₁) as an AS agentand the resulting mixture is kneaded. Next, a mixed composition (H₁) forH layer is prepared in the same manner as in Example 1. Furthermore,linear low-density polyethylene (a₁₉) is prepared as a resin for R layerand ethylenevinyl acetate copolymer (a₂) is prepared as a resin for Slayer. These resins are thermoplasticized and melt mixed at a cylindermaximum temperature of 220° C. by the four extruders (for respectivelayers of M, H, R and S), respectively: an extruder having a screw of 50mm in diameter (L/D=37) and an injection port at the position of L/D=8from the tip portion, an extruder having a screw of 40 mm in diameter(L/D=29), an extruder having a screw of 40 mm in diameter (L/D=37) andan injection port at the position of L/D=8 from the tip portion, and anextruder having a screw of 40 mm in diameter (L/D=37) and an injectionport at the position of L/D=12 from the tip portion. In this case, fromthe injection ports of the extruders for R layer and S layer, twoanti-fogging agents of glycerin monooleate and diglycerin monooleate areinjected so that each of the layers contained the anti-fogging agents inan amount of 1.5% by weight each and totally 3.0% by weight and arekneaded with the resins. Respective kneaded products are extruded froman annular die (die slit: 0.8 mm) having 7 layers of 4 kinds and rapidlycooled by a water cooling ring provided at the position of 5 cm from thetip of the die which uniformly discharges water to obtain a raw film of180 mmφ and 35μ thick (Run No. 70 in Table 26). Various raw films of RunNos. 71-72 in Table 26 are obtained in the same manner as above withchanging only the thickness.

Unevenness (in the circumferential direction) in thickness of theresulting raw films is within ±2%. Each of these raw films is passedbetween two pairs of carrying nip rolls and take-off nip rolls, wherethe films are heated to 45° C. by hot air and then air is introducedinto the films as they are and the films are continuously inflated bythe rectification contact guide to stretch them to about 3.2-3.6 timesin length direction and about 3.2-3.7 times in width direction. Thestretching terminated portion is cooled by an air ring from which coldair of 18° C. is jetted, folded by a deflator, and taken off by niprolls and air of 60° C. is blown against the film and the film is shrunkby 15% in length direction and by 40% in width direction in a zonebetween two pairs of inlet nip rolls and outlet nip rolls, speed of thelatter being slower 15% than that of the former and simultaneously thefilm is subjected to heat setting stabilization treatment and edgeportions of the film are slit to separate into two films, which arerespectively wound up under a constant tension to obtain desired filmshaving a given thickness. Similarly, the films of the given thicknessare obtained using raw films having the compositions and theconstruction of layers of Comparative Run Nos. 27-31 shown in Table 26(3.0% by weight of the anti-fogging agent (same as used in Run Nos.70-72) is injected into SBC layer and S layer in Comparative Run Nos.27-31). Characteristics of the resulting film are shown in Table 27. Thefilms of Run Nos. 70-72 are all excellent in stretchability andespecially, even in the case of final thickness of 5μ of Run No. 70, thefilm formation could be very stably performed with three punctures ofbubble per 1 hour. On the other hand, film could be formed inComparative Run No. 27, but many punctures, namely, 40 puncturesoccurred per 1 hour and film formation could not be stably performed.

The films of Run Nos. 70-72 are excellent in all of the characteristicsand especially high in tear strength and it is a surprising effect thateven the extremely thin film of 5μ showed a value of 190 g. Moreover,they have high stiffness which shows the rigidity of the film and aresuperior in running properties on packaging machine.

In the same manner as in Example 13, wrapping is carried out with eachof the films in Table 27 by the wrapping machine (pillow type andelevator type) for stretch wrapping used in Example 1. When the films ofRun Nos. 70-71 are used, wrapping are easily obtained with occurrence ofno creases even without using a simple shrink tunnel which dischargeshot air and no break occurs. Furthermore, stretch wrapping by handscould be easily accomplished with no break. Even after transportationand Stacking of the wrap, no great loosing of the film occurs. Even whenobjects having sharp projections such as frozen lobsters and frozenfishes are wrapped without using the simple tunnel, break does not occuror holes does not propagate even if it occurs in case of using the filmsof Run Nos. 70-72, though break occurs frequently in case ofconventional films. With reference to the films of Comparative Run Nos.27-31, objects having no projections could be satisfactorily wrappedwith the films of Run Nos. 29 and 31 only when the objects are wrappedwithout using a simple tunnel while the objects could not besatisfactorily wrapped with occurrence of many breaks in the case ofusing the films of Comparative Run Nos. 27, 28 and 30. Furthermore, whenobjects having projections are wrapped, many breaks occur in all of thefilms of Comparative Run Nos. 27-31 and they propagate and thus,satisfactory wraps could not be obtained.

As explained above, the films of the present invention have far moresuperior features than conventional films in the conventional use ofshrink films and especially, even when the films are made to extremelythin films as compared with conventional films, such extremely thinfilms maintain sufficient practical characteristics.

                  TABLE 26                                                        ______________________________________                                        Layer    Run No.                                                              construc-                            Compara-                                 tion of                              tive                                     raw film 70        71        72      27                                       ______________________________________                                        The first                                                                              (S layer) (S layer) (S layer)                                                                             (S layer)                                layer    a.sub.2   a.sub.2   a.sub.2 a.sub.2                                  μ     3         5         7       3                                        The second                                                                             (R layer) (R layer) (R layer)                                                                             (SBC layer)                              layer    a.sub.19  a.sub.19  a.sub.19                                                                              M.sub.5                                  μ     4         5         7       12                                       The third                                                                              (H layer) (H layer) (H layer)                                                                             (H layer)                                layer    H.sub.1   H.sub.1   H.sub.1 H.sub.1                                  μ     2         3         4       4                                        The forth                                                                              (SBC      (SBC      (SBC    (SBC                                     layer    layer)    layer)    layer)  layer)                                   μ     M.sub.21  M.sub.21  M.sub.21                                                                              M.sub.5                                           17        24        34      13                                       The fifth                                                                              (H layer) (H layer) (H layer)                                                                             (S layer)                                layer    H.sub.1   H.sub.1   H.sub.1 a.sub.2                                  μ     2         3         4       3                                        The sixth                                                                              (R layer) (R layer) (R layer)                                                                             --                                       layer    a.sub.19  a.sub.19  a.sub.19                                         μ     4         5         7                                                The seventh                                                                            (S layer) (S layer) (S layer)                                                                             --                                       layer    a.sub.2   a.sub.2   a.sub.2                                          μ     3         5         7                                                Total                                                                         thickness                                                                              35        50        70      35                                       (μ)                                                                        ______________________________________                                        Layer    Run No.                                                              construc-                                                                              Compara-  Compara-  Compara-                                                                              Compara-                                 tion of  tive      tive      tive    tive                                     raw film 28        29        30      31                                       ______________________________________                                        The first                                                                              (S layer) (S layer) (S layer)                                                                             (S layer)                                layer    a.sub.2   a.sub.2   a.sub.2 a.sub.2                                  μ     5         7         5       7                                        The second                                                                             (SBC      (SBC      (SBC    (SBC                                     layer    layer) M.sub.5                                                                          layer) M.sub.5                                                                          layer) M.sub.5                                                                        layer) M.sub.5                           μ     17        25        5       7                                        The third                                                                              (H layer) (H layer) (H layer)                                                                             (H layer)                                layer    H.sub.1   H.sub.1   H.sub.1 H.sub.1                                  μ     5         7         3       4                                        The forth                                                                              (SBC      (SBC      (SBC    (SBC                                     layer    layer) M.sub.5                                                                          layer) M.sub.5                                                                          layer) M.sub.5                                                                        layer) M.sub.5                           μ     18        24        24      34                                       The fifth                                                                              (S layer) (S layer) (H layer)                                                                             (H layer)                                layer    a.sub.2   a.sub.2   H.sub.1 H.sub.1                                  μ     5         7         3       4                                        The sixth                                                                              --        --        (SBC    (SBC                                     layer                        layer) M.sub.5                                                                        layer) M.sub.5                           μ                         5       7                                        The seventh                                                                            --        --        (S layer)                                                                             (S layer)                                layer                        a.sub.2 a.sub.2                                  μ                         5       7                                        Total    50        70        50      70                                       thickness                                                                     (μ)                                                                        ______________________________________                                    

                                      TABLE 27                                    __________________________________________________________________________                  Run No.                                                                                         Compara-                                                                            Compara-                                                                            Compara-                                                                            Compara-                                                                            Compara-                                              tive  tive  tive  tive  tive                  Characteristics                                                                        unit 70    71    72    27    28    29    30    31                    __________________________________________________________________________    Haze     %    0.5   0.7   0.7   0.6   0.6   0.7   0.7   0.8                   80° C. shrinkage                                                                %    36    36    37    30    31    30    33    35                    Tensile break                                                                          Kg/mm.sup.2                                                                        10.1  10.4  10.5  7.9   8.1   8.0   8.0   8.1                   strength                                                                      Tensile break                                                                          %    280   290   340   200   210   260   230   260                   elongation                                                                    Stress at 100%                                                                         g/cm 150/50                                                                              200/60                                                                              280/100                                                                             160/70                                                                              230/90                                                                              330/120                                                                             240/95                                                                              320/130               elongation                                                                             width                                                                (length direction/                                                            width direction)                                                              Stress at 200%                                                                         g/cm 230/100                                                                             340/140                                                                             520/210                                                                             330/110                                                                             480/150                                                                             650/250                                                                             450/170                                                                             600/250               elongation                                                                             width                                                                (length direction/                                                            width direction)                                                              Sealing  °C.                                                                         85    85    84    85    85    85    86    85                    temperature                                                                   Heat resisting                                                                         °C.                                                                         153   156   157   153   155   155   155   155                   temperature                                                                   Anti-fogging                                                                           --   ⊚                                                                    ⊚                                                                    ⊚                                                                    ⊚                                                                    ⊚                                                                    ⊚                                                                    ⊚                                                                    ⊚      property                                                                      Sealability                                                                            --   ⊚                                                                    ⊚                                                                    ⊚                                                                    ∘                                                                       ⊚                                                                    ⊚                                                                    ⊚                                                                    ⊚      Tear strength                                                                          g    190   180   180   7     9     16    15    25                    Stiffness                                                                              mg   11    20    29    3     5     8     10    17                    Thickness of film                                                                      μ 5     7     10    5     7     10    7     10                    Stretchability*                                                                             ∘                                                                       ⊚                                                                    ⊚                                                                    x     Δ                                                                             ∘                                                                       Δ                                                                             ∘         __________________________________________________________________________        ⊚:                                                               The number of punctures of bubble (per 1 hour)                                1 or less                                                                   ∘:                                                                  The number of punctures of bubble (per 1 hour)                                2-5                                                                     *   Δ                                                                         The number of punctures of bubble (per 1 hour)                                6-15                                                                        x:                                                                              The number of punctures of bubble (per 1 hour)                                16 or more                                                          

Comparative Example 1

Raw films having the compositions of respective layers and theconstruction of the layers as shown in Table 28 are prepared in the samemanner as in Example 1 with adding the same additives in the same amountas in Example 1 to the first layer and the third layer (Comparative RunNos. 32-36). It is attempted to subject these raw films to coldstretching in the same manner as in Example 1, but they could not becold stretched at all and are punctured only by attempting to inflatethem to 1.5-2.0 times in width direction for introducing air into thebubble. Therefore, the raw films of Comparative Run Nos. 32-33 arestretched to 4 times in length direction and 4 times in width directionat a stretching temperature of 115° C. to obtain films of 10μ thick.With reference to Comparative Run Nos. 34-36, the raw films melted justbelow the die in preparation thereof and when the temperature reachesabout 180° C., air is introduced into the tube to directly prepare aninflation bubbles, which are cooled to obtain films of 13μ thick.Characteristics of the resulting films are shown in Table 29.

The resulting films of Comparative Run Nos. 32-33 are inferior intransparency and have a shrinkage of about 10% at 80° C. Further, theyare inferior in sealability (narrow in temperature range). The shrinkwrapping test of Example 1 is conducted using these films to find thattight wrapping with no creases could not be performed unless temperatureof the shrinking tunnel is 120° C. and passing time is about 5 seconds.(As mentioned in Example 1, satisfactory wrapping could be performedwith the films of the present invention under the conditions of 90° C.and 2 seconds.)

The films of Comparative Run Nos. 34-36 are also inferior intransparency and sealability, and small in stress at elongation, but lowin stiffness. When stretch wrapping (by wrapping machine) as carried outin Example 1 is carried out using these films, creases remained, finishis unsatisfactory, sealability is inferior and besides, the tucked filmpeels off and thus, only such wrapping as having problems could beperformed. Moreover, the films are inferior in recovery from deformationagainst projections and permanently deformed. Furthermore, stretchwrapping (both the wrappings by machine and hands) with the films ofComparative Run Nos. 32-33 is impossible.

                  TABLE 28                                                        ______________________________________                                        Compar-      Compar-  Compar-  Compar-                                                                              Compar-                                 ative        ative    ative    ative  ative                                   32           33       34       35     36                                      ______________________________________                                        The first                                                                             a.sub.2  a.sub.3  a.sub.2                                                                              a.sub.16                                                                             a.sub.2                               layer   (15)     (20)     (100)  (100)  (30)                                  (%)                                                                           The     a.sub.3  a.sub.2  --     --     c.sub.2                               second  (70)     (60)                   (40)                                  layer                                                                         (%)                                                                           The third                                                                             a.sub.2  a.sub.3  --     --     a.sub.2                               layer   (15)     (20)                   (30)                                  (%)                                                                           ______________________________________                                    

                                      TABLE 29                                    __________________________________________________________________________                  Run No.                                                                       Comparative                                                                          Comparative                                                                          Comparative                                                                          Comparative                                                                          Comparative                         Characteristics                                                                        unit 32     33     34     35     36                                  __________________________________________________________________________    Haze     %    2.0    2.3    2.2    2.0    3.0                                 80° C. shrinkage                                                                %    12     10     Did    Did    Did                                                             not    not    not                                                             shrink shrink shrink                              Tensile break                                                                          Kg/mm.sup.2                                                                        10.2   9.3    2.5    6.0    6.5                                 strength                                                                      Tensile break                                                                          %    150    130    450    600    330                                 elongation                                                                    Stress at 100%                                                                         g/cm 940/400                                                                              930/420                                                                              170/90 130/90 300/120                             elongation                                                                             width                                                                (length direction/                                                            width direction)                                                              Stress at 200%                                                                         g/cm --/--  --/--  230/100                                                                              260/100                                                                              450/130                             elongation                                                                             width                                                                (length direction/                                                            width direction)                                                              Sealing  °C.                                                                         87     100    87     100    87                                  temperature                                                                   Heat resisting                                                                         °C.                                                                         98     110    85     110    100                                 temperature                                                                   Anti-fogging                                                                           --   Δ                                                                              x      ⊚                                                                     x      ∘                       property                                                                      Sealability                                                                            --   Δ                                                                              x      x      x      Δ                             Tear strength                                                                          g    10     22     50     300    100                                 Stiffness                                                                              mg   12     16     6      20     6                                   Thickness of film                                                                      μ 10     10     13     13     13                                  __________________________________________________________________________

Comparative Example 2

Raw films of Run Nos. 37-39 having the compositions of respective layersand the construction of the layers as shown in Table 30 ate prepared inthe same manner as in Run No. 10of Example 1. These raw films aresubjected to the same cold stretching and heat setting stabilizationtreatment as in Example 1 to obtain films of 10μ thick.

All of the raw films of Comparative Run Nos. 37-39 could be coldstretched and stably formed into films. The film of Comparative Run No.37 is superior in transparency, but inferior in sealability (narrow intemperature range) and has little stiffness. The film of Comparative RunNo. 38 is superior in transparency, but inferior in sealability and hasno stiffness as the film of Comparative Run No. 37. When stretchwrapping test is conducted as in Example 1 using the films ofComparative Run Nos. 37-38, only such wrapping as those having creasesand inferior in finish could be performed and sealing is insufficientand the tucked film peeled off. Besides, since the films have nostiffness, sticking of the films to the rolls in the wrapping machineoften occurs.

The film of Comparative Run No. 39 is superior in transparency and insealing range, but when the sealed portion is pulled, the surface layerreadily peeled off. In addition, tear strength is lower (18 g) than 74 gof the film of Run No. 34. When the aforementioned stretch wrapping testis conducted, the wrapping is possible at low speed packaging, but whenwrapping is carried out at a high speed of 100 wraps/min, break oftenoccurred upon contacting with edged of tray or contents. Anti-foggingproperty is in the grade of "Δ". When the content has projections, thefilm is readily torn and satisfactory wrapping could not be attained.

                  TABLE 30                                                        ______________________________________                                        Layer                                                                         construc-                                                                              Run No.                                                              tion of  Comparative Comparative Comparative                                  raw film 37          38          39                                           ______________________________________                                        The first                                                                              (SBC layer) (S layer)   (S layer)                                    layer    M.sub.1     a.sub.2     a.sub.2                                      μ     90          9           9                                            The second                                                                             --          (SBC layer) (H layer)                                    layer                M.sub.1     H.sub.1                                      μ                 72          4                                            The third                                                                              --          (S layer)   (SBC layer)                                  layer                a.sub.2     M.sub.9                                      μ                 9           63                                           The forth                                                                              --          --          (H layer)                                    layer                            H.sub.1                                      μ                             4                                            The fifth                                                                              --          --          (S layer)                                    layer                            a.sub.2                                      μ                             9                                            Total    90          90          90                                           thickness                                                                     (μ)                                                                        ______________________________________                                    

Comparative Example 3

A raw film having a thickness of 160μ and having the composition and theconstruction of layers of Run No. 1 in Example 1 is subjected to hotstretching to 4 times in length direction and 4 times in width directionat 130° C. to obtain a film of 10μ thick. The resulting film has a hazeof 2.2%, a shrinkage percentage of 4% at 80° C. and a tear strength of 4g. When hand stretching is carried out with this film, a large amount ofnecking (unevenness in thickness) occurs in the direction of stretchingand this is not desired. Moreover, creases which occurred in thewrapping could not removed and the film is readily torn. Besides,recovery from deformation is extremely inferior.

INDUSTRIAL APPLICABILITY

The present invention relates to a high-strength multi-layered filmstretched and oriented in at least monoaxial direction which comprisesat least 5 layers comprising at least one layer containing a specificmixed composition which mainly improves stretchability, a layer whichimproves elastic modulus and heat resistance of the film and which ismainly composed of at least one hard polymer selected from crystallinepolybutene and the like, an auxiliary layer which mainly furtherimproves strength of the film, a surface layer which improves opticalcharacteristics of the surface and the like, and other layers and to amethod for producing such film. The film of the present invention isexcellent in heat resistance, low-temperature shrinkability,stretchability, tear strength and impact strength and besides, inpractical wrapping properties and in addition, shows sufficientpracticality even in the form of extremely thin film which has not beenpresent. Therefore, the film has high practicality in the uses such asshrink wrapping, stretch wrapping, stretch-shrink wrapping, skin packwrapping, contact household wrapping, non-shrink wrapping, softdeep-draw wrapping and has a very high industrial applicability.

We claim:
 1. A method for producing a highly stretched multi-layeredfilm which comprises melt kneading each of resins arranged in at leastfive layers comprising a surface layer (S layer) and as inner layers atleast one base layer (SBC layer), at least one core layer (H layer), andat least one auxiliary layer (R layer), the resin for the surface layer(S layer) comprising at least one polymer selected from (A), (B),crystalline 1,2-polybutadiene and soft ethylenic copolymer ionomerresin, the resin for the base layer (SBC layer) comprising a mixedcomposition selected from (A)+(B)+(C), (A)+(B) and (B)+(C), the resinfor the core layer (H layer) comprising a polymer selected from (C), andthe resin for the auxiliary layer (R layer) comprising anethylene-α-olefin copolymer soft elastomer selected from component (B)and having a melt index of 0.1 to 10, a density of 0.870 to 0.905 g/cm³and an ethylene content of 85 to 95 mol %, or an ethylene-α-olefincopolymer selected from component (A) and having a melt index of 0.1 to10, a density of 0.905 to 0.935 g/cm³, an ethylene content of 90 to 99mol % and whose α-olefin monomeric unit has 4 to 12 carbon atoms, with aproviso that when the R layer is adjacent to the S layer, the R layercomprises a resin different from that of the S layer and the R layerbeing an ethylene-α-olefin copolymer selected from component (A), havinga density of 0.905 to 0.935 g/cm³ and a Vicat softening point 1.05 timesor more of the Vicat softening point of the S layer, said (A) layerbeing a low-density polyethylene or at least one copolymer of ethylenewith at least one monomer selected from the group consisting of a vinylester, an aliphatic unsaturated monocarboxylic acid and an alkyl esterof said monocarboxylic acid or a derivative thereof, said (B) being asoft thermoplastic elastomer having a Vicat softening point of 80° C. orlower, and said (C) being selected from the group consisting of acrystalline polypropylene, a crystalline polybutene-1, a crystallinepoly-4-methylpentene-1, and mixtures thereof, extruding the respectivekneaded resins through a multi-layer die to form an extrudate, rapidlycooling and solidifying the extrudate by a liquid cooling medium toproduce a tubular or flat raw film, and then stretching the raw film atan area stretching ratio of 4 to 30 times at a stretching temperature of30°-100° C.
 2. A method for producing a multi-layered film according toclaim 1, wherein the stretching temperature is lower than thecrystalline melting point of the polymer comprising at least one layerother than the core layer (H layer).
 3. A method for producing amulti-layered film according to claim 1, wherein the film afterstretching is shrunk by 5-80% (area) at 40°-90° C. to modify theorientation.
 4. A method for producing a multi-layered film according toany one of claim 2 or 3, wherein the rapidly cooled and solidified rawfilm is treated with 1-10 Mrad of high energy beam having an energy of100 KV-1 MV and then is stretched.
 5. A method for producing amulti-layered film according to claim 1, further comprising heating theraw film to 120° C. or lower prior to stretching.
 6. A method forproducing a highly stretched multi-layered film according to claim 1,wherein a thickness of the base layer (SBC layer) is 20 to 80% of thetotal thickness of the film, a thickness of the surface layer (S layer)is 5 to 40%, a thickness of the core layer is 5 to 50% and a thicknessof the auxiliary layer (R layer) is 10 to 70%, provided that the totalthickness amounts to 100%, (See Page 24, lines 2 to 7 of thespecification).
 7. A method for producing a highly stretchedmulti-layered film according to any one of claim 1, 2 or 3, wherein therapidly cooled and solidified raw film is treated with 1 to 10 Mrad ofhigh energy beam having an energy of 100 Kv to 1 Mv, and then isstretched.